If the Colorado Gold Rush happens in the 40s, Colorado as a state may well not exist as the area was then split between a strip in Texas (which Texas sold to the federal government in exchange for sponging off their debt IIRC), the Mexican Cession (territory which would later be part of Utah Territory) and the unorganized parts of the Louisiana Cession (the future Kansas and Nebraska Territories) - They might try to do more to keep those borders ITTL; maybe the gold rush could lead to their statehood earlier even, maybe early enough for Colorado territory not to be split off (in 1861). It really depends on how things happen (IOTL, a group of gold miners tried to set up a state of Jefferson in what became CO).
If the gold rush is early enough it could also affect the willingness/extent of a war against Mexico, since Pike's Peak country was already part of the US before the war.