Chaps,
The simplest thing to remember when painting a kilt on a figure is to paint what u see and not what you know to be there.
For my Gordon Highlanders I used a dark blue base (GW regal blue) with a dark green stripe (GW Dark Angels Green) overlaid with the finest of yellow lines. My figures are then given a Devlan Mud wash which mutes the colour further as it shades the rest of the fig.
Take a look at the image of the two highlanders in trews - they're about twice the height of a 28mm fig. Now look up the actual tartan and compare the two images. Thats what i mean.