Sorry for the delay in replying. Lotta stuff going on at home and work.

These two photos may help.

The first photo is of a "south china" mandarin. They are the ones with "red tipping" in the ground color and tend to have a muddier yellow in the circles.

The second photo is of a "sichuan" mandarin. They tend to have less tipping and generally lighter coloration.

Hope this helps.

Regards
John