Does a spell with a duration of one round end at the beginning or the end of my next turn? [duplicate]

Some spells are mostly beneficial to the rest of the party. My question is to figure out whether or not the caster benefits from this as well.

Take for example the first level spell Color Spray, which has a casting time of one action and a duration of one round:

A dazzling array of flashing, colored light springs from your hand. Roll 6d10, the total is how many hit points of creatures this spell can effect. Creatures in a 15-foot cone originating from you are affected in ascending order of their current hit points (ignoring unconscious creatures and creatures that can’t see).

Starting with the creature that has the lowest current hit points, each creature affected by this spell is blinded until the spell ends. Subtract each creature’s hit points from the total before moving on to the creature with the next lowest hit points. A creature’s hit points must be equal to or less than the remaining total for the creature to be affected.

Since the spell takes one action to be cast and then has a duration of one round, is it correct to assume that its effects take place at the very end of the caster’s turn, thus lasting until the end of its next turn as well?

The way I see it, this means that at the caster’s next turn, right before the duration ends, the enemy will still be blinded and he/she gets advantage on an attack as well.

I’d love to hear your opinions/experiences with this.

Note: This is not a duplicate, I found this question on the site as well, but this does not answer my question since in my opinion a barbarian’s rage starts instantly, so at the beginning of his turn or at the beginning of his bonus action, right in the middle of a turn, whereas a spell takes a while to cast and -then- starts.