What's a good test to determine the level one is color blind?

Color plates: Standardized testing of color vision can be performed by your eye doctor using specific color plates. Blue-green blindness is very common and usually easy to over come. Many people lead normal lives and never realize that they are color blind. Specific forms may cause more problems. A thorough evaluation by your eye doctor can determine the specific type and offer suggestions about management.

Many available: Simple Google: "Color blindness testing plates" and you will get a good sample. Otherwise any ophthalmologists office will have a set of proper color deficiency testing plates.