basically what would be easiest would be to set a series of single frame animations.. each named a particular color.. "red" "blue" "green" for example and then when you click your store color options.. it would tell the particular player shirt color or whatever to reflect the choice they made. This would instantly cause the shirt to change from whatever color it is.
There probably is a way (i just haven't bothered to look deeper) to set specific colors.. starting with white objects, then allowing C2 to dynamically change the color. This would be be a little more efficient, but I haven't done it before so I can't tell you how this is done or even if it's actually possible with C2..
The how to make a shop question is too vague.. and could be very simple or complex.. are you implying that you want this stuff to be saved and recalled later? You probably should start with doing the webstorage tutorial https://www.scirra.com/tutorials/266/we ... nformation
If you can understand the color system I explained above and understand how to do webstorage, you should be able to connect the dots to build the store how you want it.