You won't be able to apply any of the FL sales tax you paid against your CO state income tax - the two taxes are unrelated.
You would have to contact your CO state/local sales tax authority (or DMV) to see why CO "double-taxed" you on the first purchase, and to see if you qualify for some credit on the sales tax paid to FL.
When you make a large vehicle purchase out-of-state, the customary procedure is to decline paying sales tax where you purchased it (FL) and then pay it to your home state (CO) when you register it, Dealers understand and allow this in order to get out-of-state purchasers to buy from them.
The second RV purchase (a trade-in?) should have only been taxed on the difference between the value of the RV you traded-in and the one you bought.
