Applying a decorative finish, including painting, over existing render is the preferred option when refreshing the appearance of existing render as opposed to removing the existing render (which is a large undertaking and may cause significant damage to the substrate) or rendering over existing render (which can cause a range of issues relating to the strength, bond and key of the existing render).
For sound, site-batched renders which were not manufactured by Weber, they should be checked first for suitability of condition and be free from anything which may impair adhesion of the new decorative finish.