So when doing a tattoo with a lot of yellow, using a blue drop shadow or background can help to make the yellow seem brighter, even in darker skin tones.

Also leaving a little extra room for skin breaks can help to compliment the yellow and make it appear brighter and more colorful.

It comes down to color theory. You need to use colors that compliment the underlying tones of your skin in order to achieve the color and brightness you want.

For instance, yellow can be a difficult color to make "pop" even in pale skin.