Man pages matching name al_color_cmyk_to_rgb in section 3alleg5:

al_color_cmyk_to_rgb.3alleg5.en	debian 10 / allegro5-doc
al_color_cmyk_to_rgb.3alleg5.en	debian 11 / allegro5-doc
al_color_cmyk_to_rgb.3alleg5.en	debian 12 / allegro5-doc
al_color_cmyk_to_rgb.3alleg5.en	debian 13 / allegro5-doc