Hi Plodder
If you use an inkjet printer, there is - as far as I know - no way around using white decal paper, if you want to avoid the background colour to bleed through.
But you can avoid a white edge by using the colour of the subject as the background for your decal. At the picture, I have applied the white 'Red Horse' lettering to a bright red area of the car. The way I made the decal was, that I drew a large red square and filled in the white lettering - then printing the whole square at a white decal sheet. In this way I have the white letters with a narrow red frame.
If you look closely at the picture, you can see a small colour difference between the red paint and the decal, but this can be minimized by adjusting the colour at the decal - however, I was satisfied with this.
You can see, the white is a little pink due to the red paint - this is due to the decal paper itself not being 100% opaque. This could also be minimized by applying two decals on top of each other or by applying a white decal square before the decal with the lettering.
However, this technique is hard to use if your background is not in a uniform colour as in my example.
Another way is to use a laser printer with white toner. You can buy a white toner kit for some laser printers - see link - but I have not tried it myself.....yet :-)
https://www.ghost-white-toner.com/Hope, you can use some of this - and if you succeed it would be great to see the results :-)
