Question

If different colors of light have different speed than how they travel at a same speed in white light

Answer 1

Yes it is true that different colors have different speed.. But colors traveling in a particular medium determines the speed of the light..
In vacuum or normal atmosphere, all light rays travel at the same speed..
Speaking of white light, different light colors don't travel in white light, a number of colors mix up to give the white color which travels in air or any
medium.. And since the colors mix and form one color they travel in the same speed..

Hope it helped..