Bright yellow (by 3 users)

I can't imagine a setting that would cause this - It sound more like some sort of fault with the projector's blue LCD panel. (The image is created from a mix of red, green and blue light. If you loose the blue, everything will look yellow.)

Is it capable of showing any shades of blue?

Using any graphics or photo-editing software, create a solid blue image (R=0, G=0, B=255 in your colour settings) and if possible, display this full-screen. Is there any output from the projector at all when you do?

If not, it sounds like it need a professional repair.

Matt