The rainbow.vsc script colorizes the nicks on channel, using virc's 16-million-color tag.
This functionality can be switched on/off at the script settings panel, as well as adjusted to light or dark background colors. Additionally, it allows for outputting rainbow colored text. Example: /rb ff0000,ffff00,00ffff, This will look like a rainbow. The first three hex triplets are the start, middle and end color in the RRGGBB notation used in HTML. It's currently fixed to three triplets, although at a later stage that will most likely change.