Staining watercolours will immediately absorb into the first few layers of the watercolour paper before the water has had a chance to evaporate. These colours, once applied, are difficult to remove so that it isn't possible to get back to the white of the paper, this may be a bit of a nuisance if you have made a mistake. Beginners should probably try to avoid using them. Staining colours mix extremely well with other staining colors, but when mixed with non-staining colours they have a tendency to stain the non-staining color and can dominate the overall color of the mixture. Staining colours tend to be the newer colours rather than the traditional inorganic colours. Viridian and ultrmarine blue both lift well. Windson & Newton produce a lifting preparation which will help windsor & newton (practice on a scrap paper first)

Non-staining   Staining
Lemon yellow   Winsor Yellow
Madder Lake   Scarlet Lake
Cobalt   Winsor Red
Ultramarine   Permanent Alizarin Crimson
Yellow Ochre   Winsor Violet
Naples yellow   Winsor Blue
Burnt sienna   Winsor Green
Raw sienna   Aureolin
Indian red   Cadmium Lemon
 Viridian   Cadmium Scarlet
Sepia   vandyke brown
Terre verte   phthalo turquoise
Burnt umber   permenant sap green
Raw umber   Payne's grey
    Hooker's green
    Prussian Blue

+ others there are more staining than non-staining colours

check on the Windsor & Newton colour chart