This should say "Build hotels on EVERY property of at least 2 color sets during one game."
It's not all that complicated to get, it just takes time. Have at least 2 players and let the main account going for the achievement get 2 full color sets (example: brown and light blue). I would suggest using the cheapest properties you can get as it gets expensive quickly. Then work on upgrading all the properties to houses then hotels. Once you buy your last hotel the achievement will pop.