"Watch those colors."

Translation: Dívejte se na ty barvy.

[dsarkarati]

"Watch" is an odd way to react to colors. I can't imagine a situation where one would watch colors. "Look at" is more natural.

[kacenka9]

Well, not when the colors are changing in front of your eyes

[JBHayven]

What about "Podívej se na ty barvy"?

[kacenka9]

That would be "Look at those colors". PODÍVAT suggests a one time thing. You look and you are done. DÍVAT suggests it takes some time.