Hi Mary
Here's how tartan paint. It's been about a year since I painted it.
I painted the entire tartan medium green and shaded completely. Then I
used darker green to paint thicker stripes into the shape of a cross,
which edges were later outlined a thin line of even darker green. Then I
used light green to produce a lighter line in the middle of the dark
painted lines and made the top lighter. After a perfect drying, I darkened
the whole tartan from the bottom by vash, devlan mud and badab black from
Citadel. Then various corrections of the repair and it was done. The lines
in the folds of the Tartan of are nonadjacent and therefore it looks
natural. That's about all.
Jan