find shortest path of R,G,B Graph

Let G=(V,E) be a directed graph, ω:E→R a weight function, and s,t∈V a pair of different nodes. It’s given that G doesn’t have a negative cycle Each edge has the color R or G or B .Find the shortest path under the condition : 1) we can use green edge after using at least one red edge 2) we can use blue edge after using at least one red edge and at least one green edge . the shortest path do not have to be colorful.