The orange is for the, "Original DISC" system.
"The Original DISC 209 Muzzleloader Primer Ignition System makes loading and shooting easier...We invented dependable DISC™ ignition in 1997...Fits the Knight Original DISC"
The red is for the updated, "Full Plastic Jacket" DISC system.
"We invented dependable DISC™ ignition in 1997—black powder shooters called it “the best ignition system on the most innovative muzzleloader of our time.” But we didn’t wait for the competition to catch up, so our DISC™ ignition evolved into the Full Plastic Jacket 209 Muzzleloader Ignition System...Fits all Knight models made since 2004, including the MHS DISC Extreme, DISC Extreme, Wolverine 209, Bighorn, TK2000, or USAK (manufactured after 2003)..."Attached image is of the latter showing the bolt geometry that should be pretty telling.
Wonder if
@Sabotloader has any cool history/facts about the differences.