Permanence in the main refers to lightfastness. Some of the most vivid pinks and violets in Designers Gouache are only moderately durable and are more suitable for designers’ artwork than fine artists who usually require greater permanence.
The permanence of a colour is described by Winsor & Newton using the ratings AA, A, B and C. AA means extremely permanent and C means fugitive, or transient. Some fugitive colours may fade within months.
For permanent paintings it is recommended that only AA and A colours are used, as these are not expected to fade. For colours with a B rating (such as Light Purple) or C rating (such as Opera Rose), fading over a 10 year period would not be unexpected.