Any thoughts out there on the easiest colour to touch up stone chips etc., without it showing?

I guess one of the 'solid' colours - White - Red - Black - Yellow? And obviously assuming that you've got the right touch up shade!

Assuming you have the right shade, technique is more important than colour. I find a signwriter's mop works very well, allowing you to put just the right amount of paint "in" the chip and not all round. You can use a sharpened matchstick though on very tiny chips.

Most people seem to fail to thoroughly mix their paint, so even the correct code can turn out looking wrong.

Any colour can be touched up without it showing if you have the correct shade of paint. What I do is build up the chip with several layers applied with the point of a cocktail stick.

When it is fully dry, sand it flat with 3000 grit wet and dry paper that has been soaked, ensuring the panel is wet too. You will now be left with a very dull spot on the paint, much bigger than the original chip but the chip will have gone. You just need to polish the area (its easier to machine polish) to bring back the shine.

I was able to do my silver Octy quite well but the Steel Grey Fabia looked terrible but that was my fault no doubt !