Well, thats my idea. Instead color underline with text color, make underline color independent. eg: my name in red and underline in blue;
( i think it would be something like this: [c=4][u=2]my messenger name here[/u][/c] )

well, thats it. ^^
all the best.

It's a nice idea and sounds simple -- but it's not simple at all.

The standard underline is a font decoration.  The program asks Windows to draw text using specified font, color and with or without underline.  The program can then forget all about the underline and Windows will do all the work -- positioning the underline correctly, figuring out exact widths of variably spaced characters, not underlining spaces and punctuation, and so forth. 

Unfortunately, this facility treats the underline as part of the font and draws it in the same color.  The only way to get a colored underline is to draw it yourself, which requires doing all of the above yourself too, making it a pretty complex task. 

In case of Plus! it may be an impossible task, as the text is most likely drawn by code in Messenger itself.

So, get your point.  Well, i don't want to be a bit imprudent, but there isn't anyway to make it? well, when i read your post, i thought something like this: let Windows do all dirty work, like draw underline at correct position, things like this. then, colorize only the drawed underline. well, i know that for me can sounds simple because i don't understand much of programing languages. is isn't anyway to do this, at least i've suggested ;D thanks for the answer, Adeptus.

I confirm what Adeptus said. It's not something that Messenger Plus! can do unfortuantely. Thanks for the suggestion though .