I don't have a whole lot of experience with this but have done a bunch of research in TX.
Tax liens always take first position. When the property is sold I believe those liens are dissolved. They would have had their chance to get the property back when the tax lien was initially filed.
The way to make your money back that I have been considering, is to do bare minimum for the neighborhood to get the house rented. Keep it rented for a few years to let the redemption period laps and then flipping. In Texas, the redemption period is 6 months unless there was a homestead exemption on the house in which case it becomes 2 years. I don't know what Colorado's redemption period is.
Be careful. I know someone here in TX who was planning a flip and waited the 6 months and got the house ready. The title company wouldn't give clear title because they were concerned that the owner or heir may claim that the house should have been homesteaded even though the paperwork was never filed. I am not sure about the legality involved in this and the guy was eventually able to find a title company that would supply insurance and clear title but something to be aware of.