Someone more anoraky than me will be along with the answer to this shortly I'm sure.
The original hoop on my '97 900's was (is- I kept it along with all the other original parts for bike should I ever want to return it to standard) the same colour as the frame but in homage to the original (and along with it the 888 the frame was based on) I bought another and painted it a close match to the yellow.
However, I'd already changed the rear shock for a Nitron which has their trademark turquoise spring so was never going to match- personally I like the contrast but I agree, if your shock has the original yellow spring then it would look nicer if the hoop was the same shade.
After getting the ten year old Nitron back from a service:
In situ but the flash has lightened the yellow:
Almost together:
