The sampleImage Expression method should do the trick for you. More info here in the doc here->
http://help.adobe.com/en_US/AfterEffects/9.0/WS3878526689cb91655866c1103906....
There are links to examples which will guide you further.
Instead of using Fill or Tint, see if Tritone will get you a more believable look. Let us know if you have specific Qs.
Good Luck
RoRK
Intensive AE & Mocha Training in Singapore and Malaysia
Adobe ACE/ACI (version 7) & Imagineer Systems Inc Approved Mocha Trainer