So... I trawled the web for a mosaic sock pattern, and eventually gave in and ordered "More Sensational Knitted Socks".
And then I found this pattern....!
Even if this is not a mosaic pattern (and I confess I don't know), it is the "look" I have been searching for. Sock pal - prepare yourself for a pair of rainbow socks!
I am stalking the postman now - I can't wait to start knitting these!