New lavender bed advice

Hi, I have been inspired by a gorgeous large lavender bed in the south of France, and I want to plant up the two very hot beds that span the front of my house, either sides of the front door with two big lavender beds. It's south facing and poor sandy soil. My question is this: should I go for just one variety, or a few different ones, so a patchwork of colours? (Lilac, purple, pink). If one colour, I fancy a mid blue, rather than very dark purple or pale lilac. Any suggestions? Thanks