Reducing DECAL scale

There exists special transparent and white papers for printing water decals. These are either for ink or laser printers. You just print it and spray with colourless aerosol.
However, there are some problems, for example, if you want to have a decal with a light colour which should be applied to a dark colour background and the background should be visible inside the decal emblem- in this case you must use transparent decal paper and first print the emblem by white colour (two or three times to the absolutely same place - such a function is available in related printer) and then reprint it by the colour decal emblem itself. However, as far I know, now no printer printing white colour exists. Some such printers existed before but they are not produced so far. I advise you to contact some people/forum related to plastic kits (of planes, cars, etc) where this topis is very hot.