I have one that does the same thing. Sometimes it has a red and a striped flower at the same time.

I have some called 'Confetti' that do that. Here's a link to my post from last year.
Jim

Here is a link that might be useful: Three different colors on one plant

Almost all of that irregular coloration in flowers is very unstable and will often produce as much as 10%-15% of solid colored blooms. There is an iris called BATIK and a perennial geranium called SPLISH SPLASH that has the same color pattern. There are several pelargoniums like this, including STARBURST RED, CONFETTI and DESIGNER PEPPERMINT TWIST. Sometimes you will even get a flower head that has some solid colored florets and some with the striping. Very cool.