What part of Colorado used to belong to Texas?

Question

Specifically what CO cities, if any, used to belong to Texas?

Answer 1

No part of colorado ever belonged to Texas.

Most of what is now Colorado, was bought from France in 1803 in the Louisiana Purchase. The remainder was ceded to the U.S. by Mexico in 1848 under the Treaty of Guadalupe Hidalgo following the Mexican-American War.

Answer 2

On the other hand, if you look at
http://en.wikipedia.org/wiki/Texas_Republic
you will see that the area disputed with Mexico (lower map is clearer) did run up into Colorado. A major clue that this was likely is the date (1848) of the Mexican Concession.