There is not a special fee to e-file a CO return. If you use online TurboTax, any paid version will include a fee for federal and a fee for a state return. The fee is for using the software---it is not a fee to e-file.
If you use the CD/download, there will be a fee to e-file any state return (except for NY) ---that fee is $20 and it increases to $25 March 1.