True........
Sabots are color coded to designate what diameter bullet vs what diameter bore. For instance: black is for a 45cal bullet used in a .50cal gun and green is for a .44cal bullet used in a .50cal gun. However that is the extent of the coding - it's not like you are fine tuning the actual sabot diameter to a particular bore.
This site has a good description/picture of these codes. By the way, these MMP sabots are the best on the market:
http://www.mmpsabots.com/
"Every moving thing that liveth, I give unto you as meat" (Gen 9:3)
Trust God..........but keep your powder dry!