Question

which frog light coloured skin or dark coloured skin have most suitable characteristics for survival

Answer 1

I would say dark colored skin because then it can blend easier into its surroundings (like the mud). But it depends on where it lives. See a frog living in the rainforest would be better if it was light colored (like a light green), but other than that most would be better dark.

Answer 2

It could actually be both: For example, the light colored skin will help blend in with the leaves. Although the dark colored skin could blend in with dirt mud and leaves, serving as camouflage... All in all, I would recommend the dark skin, it can blend in with more things.
Hope this helps :)