How can I fade the screen in a truecolor graphics mode?

Description

How can I fade the screen in a truecolor graphics mode?
With great difficulty :-) There is no such easy trick as just altering the palette, so you will have to repeatedly redraw the image in a lighter or darker form. You could draw black translucent rectangles over the screen to darken it down, or use draw_lit_sprite() to tint a bitmap while copying it to the screen, but be warned that these operations are expensive and will require a fast PC!

Also, have a look at http://www.allegro.cc/ for add-on packages (notably FBlend v0.5) that attempt to make this operation as fast as possible.