Does exactly what it says on the tin. A great, easy, fix for anyone creating Spectrum games using MPAGD or AGD and finding screenshots of people playing your games with "the wrong colours" (Hopefully later releases of MPAGD and AGD will have ULA+ disabled by default, or at least set to "normal Spectrum" colours). 

(Can also be used by people who have downloaded / purchased a Spectrum game to find that the ULA+ colours are adversely affecting the playing experience).