u,v Coord Question

Ah, so your original problem was due to the filtering effect on non clamped textures, your description makes a lot more sense with hindsight.

For single color I would try setting all the coordinates to .5,.5.



Try positioning the quad half a pixel along and half down, the following illustrates a method of positioning sprites to acheive perfect 1:1 ratio of pixels to texels for zero filtering with 2D work :

http://www.blitzbasic.com/codearcs/codearcs.php?code=773