Yes you can get purple rugby boots, it is used as the base colour or as an accent, often combined with bright green or lime. Puma's V range of boots and Kooga's EVX are some of the more common places you'll see purple used for rugby. If you are after a pair check out those available below.
Covering a range of hues of colour between red and blue, purple comes from mixing red & blue in varying degrees. Many would say indigo and violet are purple, but not by the strict definition, shades of purple do include magenta and heliotrope.
Purple is often associated with nobility and royalty, something that comes from Tyrian Purple only being available to those who were well off in the past. You don't have to be the King or spend a fortune nowadays for a pair of purple boots though.