Can co tax our idaho income due to 1 day in co during road trip where we won at co casino and will file co st return due to that win?

You will report your CO casino winnings on your federal return (that is where you enter the W-2G) and on your ID return (the W-2G flows to your ID tax return). As a resident of ID, your earnings are taxed by ID no matter where they come from.

Since you won the money in CO, it is also taxable in CO. Depending on how much you won and whether the casino withheld CO tax, you may have to file a CO tax return.

If you have to file a CO non-resident return and pay CO tax, ID will give you a credit (against your ID tax) for what you have to pay to CO on the "double-taxed" income. This is how the states avoid double taxation - by allowing a state credit in your home state. 

Prepare the CO return first - this way the program will know how much CO tax will qualify for the ID credit.