no.

at the bottom of the colors dialog, you have the color index. if you right-click on white which is normally control+k0 and change it to a new color, anything sent with control+k0 is that new color. their color settings have nothing to do with yours.

you can do the same thing with say.

/color 0 1993170
which turns white into a nice shade of crap. However, mirc doesnt seem to support proper RGB colors, so you have to use $rgb(x,x,x) to get the mirc version of the rgb color code.

But again. These will replace whatever is sent using the color control code, with that color.

/color -r 0
will reset it to white.