The only other solution I can think of that would cause a bleed thru like that is too little or the wrong primer . If u do it again I'd suggest initially using a good light color primer w/ light sanding before color .
I mentioned airbrush as that's what I always use for a small area . U can shield from overspray cutting a pc of cardboard the shape of the upper edge & hold it away about an inch & vertically just above the surface . Good to practice this before hand to get distances on another surface .