The Colorado legislative body is called the General Assembly, not the Colorado Legislature. If you refer to it as the Colorado legislature, it’s in lower case.
Most other states go by legislature as part of the proper name. It should therefore be capitalized when presented as the formal name. Example: The Kansas Legislature; the legislature in Kansas.

Legislative titles

First reference, use Rep., Reps., Sen. and Sens. as formal titles for one or more names. Do not capitalize the title when it follows a person’s name or stands alone.

  • Sen. Darth Vader, R-New Hampshire, confronted Rep. Luke Skywalker, D-Michigan, in a heated debate.
  • Darth Vader, the senator from New Hampshire, was last seen driving a white Ford Bronco.

Examples (acceptable):

  • The vice president for budget and finance will issue new funding figures this month.
  • Interior Secretary Ken Salazar will speak to CU Law School students.