Its a lot like having a if else statement versus a if in programming. If the previous statement is found, ignore all the rest (if) however, if the previous statement is found to be true, check all the others just in case they are true as well, (else if).
Ironically it can get a lot more technical than that, and depending on the situation the preference changes. For this color choosing algorithm, if I were to accomplish this in programming Id do something along the lines of a while loop, followed by the values in if else statements.
While the loop parameter is true, it will continuously check whats inside the loop, ie our else if statements, and it will do those. 
basically agreeing with the other guys here, just offering my opinion on it.
One more thing though, doing greater than or equal too might be a better option, just remember to put a limiter on the variables and make sure they are encapsulated within their value ranges, otherwise you could escape the given fields and develop a bug like phantasie17 mentioned.