As far as the IRS is concerned (i.e. on your 1040), your tax will depend first on your gain on the sale, and next on which long term capital tax rate you will owe.
Your capital gains tax rate will be 0% or 15% or 20% of the gain, depending on your other income. Please see IRS Topic 409 for information on how you determine your long term capital gains tax rate.
If you are asking about Colorado tax, that is more complicated. Please see Income Tax Topics: Colorado Capital Gain Subtraction for a discussion of how gains gains taxes are handled.
Please come back if you still have a question.
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