The A is dark and the B is a light color, kinda pink looking I guess. Why would you need to know this so bad since you use them in equal parts anyhow? Just curious......
Just a FYI, Heavy 16 is a complete formula and you need no boosters or anything with it. It also has PH buffers that keeps it VERY PH stable. It also is VERY concentrated so go easy or you will burn your plants.
Peace!