So can I reuse the part of the clay bar that I used today or do I just get rid of it?

depends how dirty it is. And what'* its texture is.

I'll have to look at it again but i think it was still smooth and mostly yellow still.

The short answer is yes. Store it in an airtight container to retain the moisture.

If the bar gets too dirty you can always use it on your wheels. Once you claybar your wheels the bar is no longer good and should be thrown away. At this point the bar is contaminated with brake dust.

Don't forget to kneed it, then you should be able to reveal a clean side.

Thanks, I'll just reuse it on the wheels next time to be on the safe side and then get rid of it.