Serious question - am I the only one who has looked at SASS and all its whizbang features, and decided that plain old CSS is just fine?
Try out the SCSS syntax (or LESS), might warm you up to it a bit more.
In the end I find that if I organize my CSS well, changing things like colors really isn't such a big deal. Like you say. Find/Replace.
Oh well. Either it will pass as a fad or I will one day be forced into the light.
In the situations where a designer provided .psds for me to transform into html/css, no I haven't had to modify anything. But then, the iteration on the design happens with the other guy, and he does it in photoshop. If a change happens, he just sends me the new asset images, and I just replace them in the repo.
The times where I'm the one doing the design work, I end up switching things up a lot. This is because I don't do my design work in photoshop, but rather in the browser with actual html/css. So even while I'm iterating on something by myself (before having even shown the client anything), I'll switch colors up constantly trying to get something I'm okay with.
I strongly advocate giving the SCSS version a try. It's straight-up CSS with all the things that should have been there in the first place.
Rather than trying to remember a previous hex, or looking it up, you can think ok, this should be the darker highlight colour - and as you say, looking later you know which colour that is.
It's not just colours - a good example is a clearfix. Rather than add it to the markup, you can add it via css, and of course if you change it, you change it once.
Personally, while I do try to take advantage of all the features of LESS, I think the biggest thing is the ability to define macros (utilizing mixins or functions). Never again do I need to write multiple rules for one style (-moz-foo, -webkit-foo, and foo) or need to remember the complicated argument order (defining gradients is vastly different between all of them).
The cost is in introducing a compile step, but the benefit is that your stylesheet becomes easy to write, easy to read, easy to modify.
The math behind layouts can also be set using variables reducing a lot of headaches while the client wants 'the left column could be a bit wider'.
I agree that it requires a lot more coding discipline than plain 'ol CSS. So much to the extent that one would be tempted to abandon it. But like all good layers of abstractions, it reduces a lot of effort in the future.