I am going to change fuel injector o rings. According RealOem RealOEM.com - Online BMW Parts Catalog
upper ring is 13641437487
and lower ring is
13647509752

But what is the difference between those to rings (besides the color) ?

I can order o rings with same specs here but the 2 oem numbers leds to just one ring:
Tätningsring 13641437487 OEM-Koder