Uncoloured limewash will change from translucent and milky to a shade of white. How bright and strong a white depends on the quality of the lime used to make it.

Coloured limewashes change from a semi-translucent liquid to their solid colour as they carbonate. You often won’t know the general colour for a couple of days after painting with it, while the long-term colour may take slightly longer to come through (depending on your drying conditions).

The Old House Store has a good background article on limewash.

You can make your own limewash from slaked lime or lime putty, but slaked lime is hazardous to handle. I can make it, but find it safer and more convenient to use ready made limewash.

I’ve been trying out linseed oil in the exterior woodwork too( the rough wood shed doors), one third linseed oil to two thirds turps and that has stood up remarkably well to the sun and rain here plus it’s also a natural product as well.