Man pages matching name set_luminance_blender in section 3alleg4:

set_luminance_blender.3alleg4.en	debian 10 / allegro4-doc
set_luminance_blender.3alleg4.en	debian 11 / allegro4-doc
set_luminance_blender.3alleg4.en	debian 12 / allegro4-doc
set_luminance_blender.3alleg4.en	debian 13 / allegro4-doc