I can only speak for the M113A2 TUAs deployed to Bosnia and not Croatia so there may be variations....
1/ were the road wheels painted white?
Yes, the entire vehicle was painted white prior to deployment. The spare road wheels carried on the trim vane were green. You could probably find a replacement road wheel in green here and there. The TUAs in Bosnia were not used for long range patrolling and for the most part went from the base to OPs within 10-15 km from the base so there was likely not a lot of wear and tear on the road wheels. I am not sure what the use of the TUA was in Croatia as far as patrolling but I suspect after one was destroyed by an RPG they were seen as high commodity targets for the Belligerent forces.
2/ were the sponsons painted? and,
Yes, as per above answer.
3/ were the track skirts used?
Yes, the shorter side skirts associated with the M113A2s were used on the TUAs in Bosnia...most had them but there were probably a few that didn't.