I don't think there is an answer to your question . The 4 parameters that you provide ( Colour , Engine, Fuel , Gears ) are mutually independent of each other and have no relation between
them. That being said no one can identify how many combinations are there as you don't fill the sample space.
For your 2nd question, again there is a very easy chance that the 300 cars that have red color
have engine size (something_else) and fuel (something_else) i.e it is easily possible that
all the cars that have engine 1.4 are having fuel as 'diesel' or 'LPG' as you dont give sufficient information.
So in this case no exact answer is possible and only a range for cars that fit you criteria can be given and that would be equal to 0-250.