Seek no more.
The icons (right) come in all main Tango! colours as well as one awesome Ubuntu Aubergine coloured one for the brand-obsessed contingent.
Plum with Ambiance is pretty swell, too.
- Hit alt+f2 and type ‘gksu nautilus’
- Navigate to the icon theme directory you’re using in
- ‘usr/share/icons/‘ and either ‘ubuntu-mono-light‘ or ‘ubuntu-mono-dark’.
- Enter the ‘status/22/‘ directory
- Extract the downloaded tarball and choose your preferred coloured icon
- RENAME it to just ‘indicator-messages-new.svg’ before moving.
- Move it. :)
Every update to the Indicator applet will replace these icons so be prepared to keep reinstalling them every so-often.
Props to the dude who created these for OMG! readers but doesn’t wish to be credited.