It is my understanding that there are three roller locked extractor springs, that I know of. The copper colored one https://www.hkparts.net/shop/pc/Extractor-Spring-For-HK-MP5-94-MP5K-SP89-9mm-5p55.htm for 9mm. The steel colored one https://www.hkparts.net/shop/pc/MP5-40-10-Factory-Correct-Extractor-Spring-7p409.htm with the bend in it for .40 caliber. And the straight steel colored one with the same shape as the 9mm https://www.hkparts.net/shop/pc/HK-Rifle-Extractor-Spring-For-All-HK-s-German-8p188.htm is for rifle calibers both 5.56X45 and 7.62X51. "G3Kurz" works for HK and has posted that all roller locks "could" use the rifle spring but that the rifle spring in the pistol caliber guns would tend to cause more extractor wear.From HK, the copper colored extractor springs are for the 9mm SMGs. The silver colored extractor springs are for the .40 and 10mm SMGs and all the rifles. There is no difference in the sliver colored springs.
James, you are far and away more knowledgeable about HKs, especially roller locks than I. What you posted about the copper springs and the K guns makes sense and I'll have to get some copper colored springs for my replacement parts box to use in my 9mm guns. As far as checking the extractor spring, my method is pull the cocking tube support handle until the face of the bolt is toward the back of the port in the receiver. Reach in with my finger and try to pull the extractor towards the port, away from the center of the bolt face. If I can move the extractor with your finger, the extractor spring is no good and I replace it. I only remove my extractor spring if it doesn't pass my finger pulling test or I am having extraction issues and I need to clean under the extractor. Which would be holding an empty shell casing and putting it on the bolt face, shaking the bolt holding the shell, the bolt falls off. It usually has taken a couple of thousand rounds of use before I would need to clean under the extractor. I have ruined a brand new spring installing it into the bolt. I have found it is so easy to ruin an extractor spring by removing/installing it. YMMV.