four colours are enough because "colours" is the noun and it is in plural. However should the sentences been without the noun (colours) then "Four is enough" would have been correct
I have tried "Of course four colors are enough" and it is wrong. So "of course" can not be as the translation of "určitě"?
My answer -- Four colors IS definitely enough -- was accepted.
I used "is" rather than "are" because it looked like the verb -- stači -- is singular. I figured that, since what I took to be the singular form was used, the actual subject of the sentence was "čtyři," not "barvy."
Did I just get lucky, or is my reasoning sound? :-)
UPDATE = = = I think I just got lucky... the form "stačí" is the same for both third person singular and plural.
What about: "Four colors are entirely enough?" I believe somwhere else urcite meant entirely or completely?
The definitions I've seen for určitě all describe certainty in one form or another. You may be confusing "určitě" and "úplně," which is pretty easy to do when you're just getting exposed to them. :-)