I have a number of foundry paints as well as GW, Vellejo and a selection of other makes.
The foundry on the whol;e are my favourite on the whole. The quality of the paint is top class and pot for pot they are better tvalue than GW. Especially dislike the latest variation of GW pot design - lid keeps popping back.
I have found some of the 3 colour pots do not have the colour difference that is required to set them apart. This seems to be more so in later colur schemes that have been introduced. I have used 3 of the napolionic range (british red, french blue and chevalier green) and there is so little betweent he three tones that it is difficult to tell them apart. I also have some of the earlier numbers as well and these have very good colour definition and paint up nicely. I like to paint with faily thick colour so the high pigment suits me down to a tee
To answer some of the points raised above - you can now purchase individual pots of colour and if you want a good yellow use the Orchre it has a very nice effect. It start with an orangy base coat and builds to a bright yellow.