Questions I need answers to

1. How do I test colours for lime tolerance? If a colour is lime tolerant, how long will this be safe for? 1000 years? 5 years?

2. Are frescoes OK out of doors in GB? Is it advised to protect an outside fresco with something like an overhanging porch?

3. If a colour e.g. viridian green is known as lime-OK, can I then buy that pigment, cheap and cheerful, at a local shop, or will it only be OK if it is ordered from specialists?

4. I've read that ultramarine blue is not too reliable in lime, especially out of doors, but have heard a specially processed product is OK. Can anyone help?
   
   

5. I am still unsure if I paint frescoes as transparent (watercolour) or opaque(oils) or a mixture of both? Any advice would be welcomed
6. Is grinding the colour necessary nowadays?