It's frustrating when it happens, but I'm trying to remain emotionally detached from the project (what with me not being the aforementioned Hooker With The Heart Of Gold and all). It's just a pain having to deal with a dozen different "can you make that blue a slightly different blue?" requests per day.
If it was an hourly thing, I wouldn't be as mildly annoyed, but I'm being paid a flat project-completed fee, so fielding dozens of minor requests for tweaks does affect my bottom line.
The only advice I can give during this phase of the project is to limit your availability. If you're working 9-5, this ain't an easy request. If not, try to only make yourself available for the minimum amount of time required to make such changes.
If you're available at all hours, you'll have to make blue-to-different-blue-and-back changes all day long. If you're only available for three hours on Thursday, not only will you find that those three hours won't have the inevitable end-of-project slack time that you'd get from being there longer, but the artist-types will get to flake themselves into a frenzy of blue-to-different-blue decisions in your absence, and hopefully you'll only have to implement the end-result of their fine design wisdom.