It's one of the things you can't do with a normal laser printer, where the colours depend on a white or light background. If you have the patience and skill, you can print on white decal paper and cut round it and/or design the logo so that it has a black outline that's easy to cut round.
You can print a reversed black outline of the logo, then fill it in with a silver of gold paint pen, then turn the decal over once you've soaked it and stick the coloured side to the headstock. There may be a slight mismatch between the headstock black and the logo black, but there's not a lot you can do about it. If the outline is thin, it normally doesn't show or matter. An example here: https://www.buildyourownguitar.com.a...l=1#post166389
But it may be easier to use a printing service, especially if you get a whole sheet of logos made up. I'll let more people more local to you make suggestions for that, but I know there have been some recommendations fairly recently in various posts.
Last edited by Simon Barden; 07-07-2020 at 06:45 PM.