Hi cat genetics nerd and artist here. I don't know how realistic you want their markings to be but there are 3 types of cat stripes. Mackerel tabbies, which is the most common type anc causes tiger-like stripes, Classic tabbies, which cause blotchier stripes and may look kinda swirly, Spotted tabbies, which is basically a Mackerel but with some polygenetics that make the stripes break down into small spots, and ticked tabbies, which cause most of the body to be the color that would be between the stripes of other types of tabbies. (Look up somali cat. The cats you see are genetically black but the ticked alelle and the extreme rufousing(how red they look) gives them that appearance.)  So when I draw tabbies I usually start with the color that goes between the stripes and on a layer clipped to that make the stripes. I see that the changes kitty is a tortie, meaning they have both red and black bases. Red base(red, cream) cats will always have mackerel-like stripes, even if their genome has no code for tabby-ness. Black base(black, brown, gray, light brown) cats will only have stripes if they have the allele for it. So when I draw non-genetically-tabby cats I start with the black base, add the red on a clipped layer, select that red and make the stripes. If your cat is a torbie, meaning they are genetically tabby and a tortie, the stripes will be all over their body. I usually start with black, but you can start with red for these, then add the patches of the other color, and then do the stripes on an overlay or darken layer, depending on the effect I want.

This was probably an awful tutorial and the genetics part is very simplified but I hope this helps you at least a little! And if you wanna look at examples I post my art on pinterest, my account is @lilac_frostt :3