The colors are set in a configuration file in the romfs, haven't opened one in quite a while but I do vaguely remember a blur level option...It is not the 3DS that has the problem... I am talking about the seccond "Green Palette". The one you switch with L+R+Y. If I add the green effect (or any other color palette) to the first layer, I don't get the blur. The first palette has no ghosting effect.
Look into the file manually, don't use GUI tools that almost invariably never give you the freedom of manual editingThanks for the answer ... I've looked into what you said and I can\t find such a thing... I am using Ultimate GB VC Injector for 3DS 1.2 and there's nowhere such option... Maybe you remember something that has to do with the injector of the GBA roms...?