I’m making decals for two custom P-51s that I’m building for my fiance and our son. One of her favorite colors is purple, which I think will look good on the yellow nose of the Mustang. Since I like Tamiya’s purple, X-16, I was wondering if it’s possible to make the lettering the same color as their paint? If so, how can I do this? I was also thinking of the lavender/purple that the chocolate brand Milka uses. If nothing else, I have the CYMK (?) for Milka’s purple.
What I do is to paint a piece of scrap plastic sheet or a dummy credit card or plastic coated advertising flyer with the paint, and then scan the image into my computer. Most graphics programs allow you to sample a color and use that color in a drawing. My printer is not calibrated, so the color may be off a little, but it is pretty close. If you trim the decal close enough it is usually not noticable.
I do much as Don does, but I tend to take my ‘samples’ directly from online images, or even from online swatches or color cards. If you’re trying to match a chocolate wrapper it’s even easier, since you should be able to find ‘true color’ manufacturer’s images on their website.
Cheers
What I have been trying to match is the paint I use, when making white or light colored decals (printed on white decal paper). Ordinarily you would have to trim them perfectly with a knife or scalpel. By setting the background color to the paint I am using, I can trim closely, if not perfectly and the border is not that visible- even the insides of letters like As and Bs seem close enough.
Yes, for dark livery colors on light background colors the photo colors are fine.
That’s exactly what I did on my recent Bo105 air ambulance. Both the SCAA logos and the tail codes & markings are printed on white decal stock, with printed ‘surrounds’ color-matched to the paints (since in 1/72 they’re really too small to trim neatly):

If you have a local printer, take your sample card to them. They will be able to match the color with their PMS (Pantone Matching System) book. That will give you the exact CMYK values when printed on white background.