If I sell my rental houses in Colorado what are the taxes

[Phillip1]

Colorado does not have a capital gains rate that is separate from the regular tax rate. The gain on the sale (sales proceeds minus your adjusted basis) is taxable at a rate of 4.63% If the property was acquired between  May 9, 1994 and June 4, 2009, you may qualify for the Colorado capital gains subtraction of up to 100,000 dollars.

See the following: https://www.colorado.gov/pacific/sites/default/files/Income15.pdf