Will Mango get more colors? Probably not.
The other big news today is the two new accent colors found on the Toshiba IS12T--namely a grey and citrus. Some people have taken this to mean that Mango itself will have these additional colors, to which we reply "probably not".
For one, Joe Belifiore has stated before that there are no new colors in "Mango" and we see no reason why that would change in the remaining builds of the OS. Second, OEMs and carriers have always had the ability to add custom accents to their devices. Case in point, my HTC Mozart from Orange UK--it literally has an accent called "Orange UK" and yes, it's different and in addition to the regular Orange (the former is darker).
That's obviously what is going on here as Toshiba wanted accent colors to match their unorthodox bright scheme--so they did. But we're going to bet you won't have any citrus in the final Mango build.