Cunningham started desining Nishiki models in 1989. Shimano 500LX was manufactured form 1990-1992 but the 1990 Colorado used the lower, 400LX group, so yours should be 1991 or 1992. The 1991 does have a "web" paint scheme that may be your spackle, but it is blue with white web. The 1992 just states metallic black or pearl white, with no mention of webs or spackles. However, the 1991 is distinguishable from the 1992 by using a straight bladed fork and neon green logos with a gold shadow. The 1992 has a traditional, curved fork and silver logos with a red shadow.

It sounds like there are a lot of replacement parts on your bicycle. The OEM shifters were 500LX. The Deore shifters may or may not be indexed. If they are trigger shifters (i.e. with separate levers for the up and down shifters) then they are indexed. Thumbshifters (where you use the same lever in different directions for the up and down shifts) can be either. The indexed thumbshifters typically have a switch on the front for setting in either index or friction mode. Older thumbshifter, without this switch are friction only. Can you post a picture to be certain?

It sounds like the previous owner put on a lot of promotional decals on his bicycle, to make it look like a pro's bike. The one decal is probably Mountain Bike Action, the name of a popular magazine, which is still in existance. Anza is probably Onza, a popular brand of secondary components, such as handlebars, stems, bar ends, pedals, etc. I'm not familar with Bike Lane Racing and the Specialized decal should be an aftermarket market too, as the only decals shown in the catalog are the downtube logo decals, the top tube model name decal, the head tube decal and the Cunningham design decal on the seat tube and forks.

I doubt this bicycle was raced. Most racers would have opted for a Deore XT, Deore DX or Deore LX equipped model.