Having spent 6 years of my life inside Buildings 10,17,18,19 and 23 in Redmond, I have spent many hours discussing the morphology of login names (or aliases).
Mine comes from the early MS standard of "your first name + first letter of your last name + second letter if still not unique". That's why billg is email@example.com.
You can often guess whether someone is an MS old-timer by the structure of their name. Obviously, the first name dominant style became unwieldy as the number of logins moved into the high thousands. First they started doing weird things to peoples first names (dropping letters), then they gave up and started giving people last name bases aliases.
Strangely enough, I had never in my life had a nickname until I started working for Microsoft. And suddenly, due to the blessing/curse of a pronounceable email name, I became...markgo. To every one. All the time. In person, on the phone or (of course) in email.
Still, at least markgo was inoffensive to me. I knew some folks who HATED their email names, yet because they were pronounceable, every one called them that any way. My favorite was a guy named John NyXXXXX, who didn't like being called anything but John. See if you can guess what his alias was :-)
On some sites where markgo is taken, I am markgo2k, which is actually a snitty reference to the fad of putting 2k after everything (Y2K, Win2K, etc).
To bring this thread full circle: at the top was some speculation as to why chromatic is chromatic. I've got a pretty good guess from my wastrel youth playing 36 hour sessions of D&D (Dungeons and Dragons for those who have never played RPGs without the help of a computer). In AD&D, Chromatic usually was the top-of-the-line. Thus, Tiamat, the baddest-ass dragon was a chromatic dragon, there's a whole series of spells working up from chromatic spray to chromatic orb.
Roll d20 to save, chromatic...