Don't worry about the replacement, updating things is always great.
Yea, xmls are always fun to edit. e.e (Next two paragraphs are completely off topic, but it's tradition to stray so...)
I remember editing the xmls in Civ5 (didn't want to install and figure out the tools to do a proper mod) because I hated the names for the Haudenosaunee (the Iroquois), as a lot of them were french names, and I always played as them, so I always saw the names. So I commented out (or deleted, I forget) the names I didn't like and tweaked some others in the English language files.
Well, the tweaks worked fine IIRC, but the names that I deleted? Well it switched to using the french files for those names (which nearly caused me to burst a blood vessel as I was editing most of the names to make them less french. It knew what I was doing and was taunting me, I swear.) Anyways, so I go through the XMLs of all the languages deleting what I wanted, then test it out. It displayed the code of the names that I deleted instead. The actual list of names were apparent kept somewhere else in the xmls (which I think I had already found too difficult to edit). Anyways, that's why I don't have Civ5 installed anymore. ^.^
(Back on topic)
As for the colors, everyone's going to have a different opinion. I personally prefer more muted colors. I can see why picking the color for *label would be difficult (good idea to separate it BTW). Red and Blue are obvious for the first two, but the third is always difficult. Greens do not catch the eye in the same way, and Yellow just bleeds into white. An argument can be made for pretty much any decent choice of color to be the 'proper' third one.
As for the strings, well, I think that's also gonna depend a lot on the author too. I personally end up with a lot of *ifs and *choices right in the middle of a conversation, so that turns a lot of stuff grey. I image that there as some that won't ever have that problem. (And don't mind their conversations being in grey.) As for which is most convenient, I'd probably have to say not including it. The highlighting for *set already helps to set off the , while the ghosting from quotes could potentially be quite an annoyance. Perhaps quotation marks could be included as an operator (+, -, = ect.)? It kinda looks good to me like that.
(Funny thing, I originally tried to tweak that by changing the color to black. That was a stupid move. Not only did I have the same problem, but I didn't know what in the world was causing it, 'cause I though I had just fixed it. I literally did the one thing that could make it more difficult. Tonight's just gonna be a derpy night for me.)