First of all, you cannot assign a whole array at once, just a single element:
KLEUR[i] := RANDOM(4)+1;
Secondly, you seem to solve the problem in a wrong way. I.e. you have, let suggest, KLEUR = array(1,1,1,1) - it's random and this vairant is possible. And you compare it to input 'A'. Seems strange to me. What do you want the user do? Guess?
It seems that if the number is not KLEUR[1] the answer is 'W' i.e. wrong... why so?
But if that logic is ok, then just do:
answer = '-';
if A=KLEUR[1] then ... 'R' else
for i:=2 to 5 do if A=KLEUR then .. 'W';
Because Case is not designed to work with non-constants which may have duplicate values like in example above. e.g. which of five '1's the case should choose? So use 'if' construction