Well, here is a general break down:
5 is best - 1 is worst
Speed/maneuverability
5. Yellow
4. Blue
3. Human
2. Red
1. Green
Firepower
5. Red
4. Green
3. Human
2. Yellow
1. Blue
Engineering
5. Green
4. Red
3. Human
2. Blue
1. Yellow
Science strength
5. Blues
4. Yellow
3. Human
2. Green
1. Red
The Hull and Shield values are going to be equal to help balance things
So generally speaking, Yellow focuses on speed, Red focuses on Firepower, Green focuses on Engineering and Blue focuses on Science.
So if we do 1 Race, I might suggest Red just because they will have the highest DPS, but it lacks in other areas.