CS, i grow Bela Lugosi, Ashwoods Dark Side and Beyond Thunderdome. These are just 3 of my purples that seem to keep their color all day and are truly some of the truest deepest purples i have seen.
Luara Harwood is another deep purple but it also has a large yellow eye zone.
If your into multi shades of purple try Michael Bennett which i also grow. It is a real beauty and never fails to impress me with its color and gobs of buds. It is also very photogenic.
