The HB C12 is a great car... You can start with
Grey or
Yellow in the rear and
Purple or
Lilac in the front. It is a little hard to say which tires you
must use because it also depends on the type of carpet, driving skills, motor etc. but these compounds will get you on track to start with. It would be better to go to your track and ask other 12th scale racers which tires they race with and then use these compounds too...
Be aware that the HB C12's rear axle has a minor problem with the JACO Prism wheels. These wheels have a -3mm offset and since the C12 axle is not adjustable you can run into a problem fitting these wheels. I have had a C12 and I have replaced the stock rear axle for a IRS version from Team Associated. You can also use a CRC rear axle or a similar type. These axles are made from graphite and will also be lighter than the stock C12 axle plus they can be adjusted in track width so you can compensate the -3mm offset of the Prism wheels.
Another part of the C12 that is very fragile are the front axles. They really DO snap like a twig when hitting the border. You can easily solve this problem by mounting a set of Asso/CRC steering blocks with a set of stub axles in steel or titanium. Trust me on this one, these modifications will make the car better.
Here are some part numbers for you...
IRS 1/12th Associated Style Large D-Ring Graphite Axle Assembly (purple)
# IRS2132P
CRC steering block front end
# 1251
CRC steel stub axle set - threaded
# 1235
Hope this will help you on track...
Joost.