Both words mean "farmer," but 'colonus' can also mean "colonist, inhabitant."
An ancient Roman farmer was a farmer, someone who grew things. If you mean the word for farmer, it could be one of three, agricola, arator, or colonus.
agricola
agricola sum, or sum agricola, or ego sum agricola agricola = farmer sum = I am ego = I
Agricola is not a verb. It is a noun and means farmer.
Farmers = Agricolae
'Agricola', from which we get the word 'agriculture'.
Translations: agri, ager
'agricola et uxor' or 'agricola et uxōris' the second is a better translation than the first
What is the difference in Latin between 'cohortis', 'cohors' and 'cohortes'?
Quod in terras est, Agricola est laetus, Et laborabit.
The Latin word agricola means "farmer" in English. To say farmers (as in the plural form) you add -ae to agricol. So, to say farmers you say "agricolae."
The prefix of "colonial" is "colon-" which comes from the Latin word "colonus" meaning farmer or settler.