Ripples, Stripes, Flakes and Fancies
As well as single "self" colours, sweet peas have all sorts of patterns and are often known as "novelties" or "fancies". This picture is of Sweet Pea Nimbus - it has a white background and an inky blue colour on the backs of the petals and a coloured rim around the petal edge, called a pictoee. This type of patterning is called "Ripple" or "Stripe".
Another example of this is Lisa Marie - it's one that divided opinion - some people love it, others hate it! It has a similar pattern of colouring to Nimbus, but in a deep maroon.
Sweet Pea Burlesque is has a different distribution of colour - its still on a white background, but the blue colouring is on both sides of the petals and goes all the way to the edge and there is no picotee. This type is known as a "flake". Other examples include Senator and Unique.