Theo R Cwithin
I cast "Baconstorm!"
This.Perhaps we should define what we mean by "dark and gritty". To some, it having means a deadly combat system. To others, it means having a forlorn and hopeless atmosphere or an absence of clear moral lines. Some sees it as having PCs that are no more special than NPCs while others see it as injecting real world societal problems into their game worlds.
For me, the OP is a little difficult to understand, because it suggests that "dark, and gritty" and "colorful" campaigns are two opposite poles on a spectrum of possible campaigns. However, IMHO, dark doesn't necessarily mean gritty, and a colorful campaign can be quite gritty. Just as a personal example of how I view the terms, Ravenloft is dark but not particularly gritty, whereas Darksun is gritty and colorful. And I'm quite sure more than a few people will disagree with me on this!
Back to the OP: That's not been my experience.