Do you mean the Tan color? I didn't think there was Sand Grey. I thought it was Dove Grey if you mean the Grey color. I haven't seen many Ti's with Sand interior.
I have a Dove Grey interior. And have Black M3 floor mats and it's fine. Pretty sure you can still get Grey though too with the BMW written on the Drivers side if you like. Mulberry sounds cool.
I've gotten my floor mats from part outs, but I'm sure that any E36 mat will fit. Bav auto has stuff like that. Though I would have a hard time paying retail.
These seem like the ones that I have:
https://www.bavauto.com/bmw-all-weat...SABEgKOUPD_BwE