Are you absolutely sure you are colour blind? I was not good on the Ishihara dot tests and was initially told by an optomotrist that I was colour deficient but passed the RAF medical with a three colour light test. Sometimes things such as dyslexia can cause problems with the Ishihara test. Might be worth seeing a specialist with regard to colour vision. Otherwise why get checked out on a sim when you could spend the money on a day VFR PPL and have a huge amount of fun?