## Different background colors on different dates in DateListPlot

I have a time series plot

DateListPlot[{1, 1, 2, 3, 5, 8, 11, 13, 17, 21}, {2000, 8, 6}] 

I would like to have a background which is white upto Aug 10 and yellow from Aug 10 on to enphasize these later days. In general: how can you have different background colors on different dates?

I think I saw this done in the documentation center, but cannot find where.

Can you suggest how to do it?

## Coloring a graph with odd number of vertices with $k$ (which is close to $\Delta$) colors in linear time

We have an undirected simple connected graph with odd number of vertices. We also know the number $$k$$ which is actually the closest odd number greater than or equal to $$\Delta$$. (So if $$\Delta$$ is even, $$k = \Delta +1$$ else $$k=\Delta$$.) i.e $$k$$ is the least odd number that is greater than or equal to degrees of all vertices.

We want to find a linear time algorithm that colors the graph with $$k$$ colors.

I am very new to graph coloring algorithms. I know that a greedy algorithm is actually linear time and can color the graph with $$\Delta +1$$. But I can’t guarantee I can color it with $$k= \Delta$$ when $$\Delta$$ is odd. Also, we probably should use all the information the question gives us. i.e using odd number of vertices somehow, but greedy algorithm don’t use this extra information.

How can I solve this?

## Complexity of list coloring $K_n$ with $n$ colors

The list coloring problem is, given a set $$L(v)$$ colors for each vertex $$v \in G$$, is there a proper vertex coloring, $$c$$, of $$G$$, such that $$c(v) \in L(v), \forall v$$.

I was wondering, for complete graphs $$K_n$$, is list coloring NP-complete? Does this change if $$\bigcup_{v \in K_n} L(v) = \{1,2\dots n\}$$?

## Do we need to follow brand colors for data visualization?

I am working on a design language project for our product. I’m currently putting together a color palette for data visualization part of the app. Based on my research on colors for visualization and careful consideration of color theory, and accessibility, I came up with a set of colors (muted color palette) that would blend well with the UI. I worked it off the brand colors. Because our primary brand colors are Orange, Grey, and Green and ours is a typical network/device management app.

So, the question is: do we need to use brand colors for data viz?

Of course, the product UI conforms to the brand colors. However, I feel the chart colors not necessarily be restricted to the brand palette for a couple of reasons:

1. The marketing team which originally came up with the brand colors would not have thought about colors that would work well for Data viz. And I think they are more of a brand guideline that’s suitable for the promotional/marketing material and for the corporate website. They don’t seem to fit the bill for chart colors. We do have secondary and tertiary colors. So some of the colors I’ve come up with are derived from the secondary and tertiary colors and I’ve reduced the saturation level so that it’s easy on the eyes.

2. It is an NMS app, orange and grey (primary brand colors) has some meanings in our app context (e.g., error, severity, others/unknown etc.,)

Should the chart colors represent the brand? Are there any guidelines on this? If someone could point me to some best practices, it would be helpful.

## Is using different colors for internal and external links OK or what?

I’d like to use different colors for internal and external text links. Please tell me if you think this is a good or bad idea.

I’m considering CSS choices on a new site/web app which will contain article pages that have a lot of internal (same site) and external (another website) linking. By providing a colour identifier the visitor will then know if the link keeps them on site or about to head off to another site.

I’ve considered box arrow icons but they look unsightly when an article has a lot of external links.

Please if you have any examples of sites/studies which demonstrate this working or failing, it would be great to hear.

Thank you

Matt

## how we choose gradient and flat colors for creatives based on the image used or attractive color?

Creating creatives for social media or blog,

we using gradient colors or flat colors for creatives.

My question is which is the correct way to do, based on the image we need to select the color or random colors we will pick.

In my view is I selected colors based on the image we used in the creative.

## Arranging Colors in a Grid; Two Dimensional TSP?

I am working on an interesting problem, which I believe can be solved algorithmically. I have a 6×8 on which I am attempting to arrange 48 color swatches, such that the transition from each swatch to its neighbor is as smooth as possible.

I can compute perceptual color differences using LAB-space encoding, so it is simple to generate a matrix of color differences. If I were attempting to simply order these colors, it would essentially be the traveling salesman problem; and I could use some heuristic solutions to get a near optimal result.

However, arranging the colors into a grid introduces a new dimension. In the interest of symmetry, we can wrap the edges of the grid so that each swatch has exactly 4 neighbors.

I have a hunch that this problem reduces to the following graph problem: Given a fully connected weighted graph of 48 nodes, find a subset of this graph such that the resulting graph is fully connected, each node has exactly 4 edges, and the sum of edge weights is minimized.

Any ideas on existing algorithms that might be helpful in solving this problem? Approximate solutions and heuristic solutions are acceptable as I imagine this problem is in EXP.

## Plot3D: Plot a piecewise function with different colors when plotting multiple function

I am plotting two functions in two variables and one of them is a piecewise function as given below. I am trying to get different colors for each of the sub-function of the piecewise function.

func1 = -(Subscript[n, 1]^2 + Subscript[n, 2]^2) + 100 cb1[[1]] = 1.1245; cb2[[1]] = 0.7153; p1 =   Plot3D[{func1,     Piecewise[{{cb1[[1]] + 100,         Subscript[n, 1] <= 5 && Subscript[n, 2] <= 5}}, cb2[[1]]] +      75}, {Subscript[n, 1], 0, 10}, {Subscript[n, 2], 0, 10},    AxesLabel -> Automatic] 

The entire piecewise function is in color blue as shown in the figure. Is there a way to have sub-functions in different colors? Also, is there way to have the origin on the bottom left?

## If you pass through the order of colors in Prismatic Wall one way, do you reverse the order of colors passing through the other way?

I set up a Prismatic Wall and a non-protected creature passes through it, say from left to right. On page 269 of the 5e Player’s Handbook, the spell reads:

“When a creature attempts to reach into or pass through the wall, it does so one layer at a time through all the wall’s layers. As it passes or reaches through each layer, the creature must make a Dexterity saving throw or be affected by that layer’s properties as described below.”

The layers are listed from Red to Violet, so the enemy passed through my wall in that order and made it through. They are now on the right side, and I have contrived a way to push them back through the wall to the left side. Do I reverse the order they encounter the layers and go Violet to Red, or do I always go Red to Violet whenever anything passes through the wall?

In other words, does a Prismatic Wall have a “sidedness” to it, and, if so, when is that sidedness established?

## How Do I Change ALL the Colors of Ubuntu 18?

I tried to customize my Ubuntu 18 desktop colors by changing all of the purple and orange (hex and RGB) values in the gdm3.css to green, but I keep seeing purple when I sign out and sign back in and I keep seeing orange highlights when I switch ‘directly’ between applications! What am I missing? Is there a better way to change colors in this OS? It even says “This stylesheet is generated, DO NOT EDIT” on top, but I edited it because I could not find a better suggestion online. It is especially frustrating because the colors get reverted back by distribution upgrades sometimes. Should I be exporting different color environment variables instead? What does the Linux community know about customizing GNOME that I don’t?