Lex Does Art N’ Stuff

I don't know if the way I draw tattoos is the most natural looking or the best way but I can show you how I do it!

The thing that will make the tattoos blend with the character in a more realistic way is the color. Tattoo ink fades and changes color a little once your tattoo is healed, and I've noticed that using a saturated color instead of pure black helps to achieve that effect. Of course, your color choices will vary a little depending on the skin tone of your character (use a darker reddish color for a character with darker skin tone, a lighter one if the character is very pale, etc), but the multiply mode will help make the tattoo design stand out regardless. You can play around with opacity levels too. Here's a side by side comparison of how the tats look if you use a brown/reddish color vs an achromatic black/gray.

It's a matter of taste, really. I don't think the 2nd image looks worse, but I like the look of the first one better because it blends with the skin tone a little. If your art style is more graphic/bold than mine, you may want to stick with bolder tattoos that stand out more than the ones I draw. For example, I don't always do this process; here's an example of tats I drew that do not blend as much with the skin: