The word ‘colours’ (alwan) in plural form appears a total seven times in the Quran (16:13, 16:69, 30:22, 35:27, 35:27, 35:28, 39:21),
Which if you haven't noticed is the same as the number of colours visible to us in the light spectrum..
There are many such examples of this kind of thing in the Quran, how many do you need to see in order to believe? The signature of your Lord and Creator, is all over the Quran :)