Okay. there's two easy ways to do this, and a hard way. The first easy way is not to. The lid assembly of the Ti is a sealed part. When I say sealed, I mean sealed with epoxy. Its not designed to come apart. Apple ships them as finished pieces, and many techs wont take them apart, simply because its a horrid bit of work. So, first option, fergit about it.

Second option. get some airbrush masking paper or film, an x-acto knife, and some transparent color glass stain. Mask the logo, cut out the shape and peel away the inner bits, leaving the apple exposed and the case protected. then, using a sable tip watercolor brush, apply several coats of the stain. Once dry, remove the mask, and bask in your colored logo.

Option three, take apart your entire machine to get the screen removed from the rest of the unit. remove the front bezel assembly without bending or crimping it (super hard) remove rest of guts from display housing. then put a piece of colored acetate behind the apple logo. then put everything back, and glue it all back together, holding the case together with c-clamps. Wait several days for the glue to cure, and you might be good.

Overall, I'd not recommend the third option. Its a lot of pain and suffering, for what some would consider a minor mod. If you simply cant live without a colored apple, go with option two, much less suffering. Hope this helps!
Electricity tastes good. No, seriously.