In the late '60s, there were three K2 models: the Holiday (intermediate), which was white; the Elite (expert), which was blue; and the XR10 (Junior racer), which was red. Graphically, they were true to the time: just a shiny topsheet, with the K2 logo and the model name in smaller letters at the tip.
Around '70 or so K2 must have engaged a "creative" ad agency, because they started coming out with what seemed at the time to be incredibly hip ads. That's also about the time (I think) they came out with the Competition, which was red, white and blue striped, and looked very sharp by the standards of the day. Shortly after that, they revamped their line into the 1, 2, 3 and 4 (and the J4, as in "Junior"). So far as I remember, they had the model written out on the tail, along with the appropriate number of black chevrons (also chevrons on the sidewall), though that might have varied during the run of the line.
The older K2 Comps are distinctive in that the red and blue stripes come together at the tip, rather than running off the end.