I would like to give my N900 screen a distinctly
yellowish cast, to make it easier on the eyes at
night, and less disruptive of my melon-tonin'.

Yes, I've tried scribbling it with a yellow highlighter
pen, but the 'ink' remained liquid and rubbed off too
soon.

A piece of yellow cellophane or similar film should work,
but I'm not sure how to make it sticky yet optically
clear (rubber cement, rolled very thin, may work).

The ideal way, though, may be altering some display code,
to give just the tint desired. Is there some n900-
related program that can do this (there's one thread giving
details about this, but it's for the n9; there's also mention
of "screen filters", overlaying a transparent image, for
Android).