Nifty. Those are like mine in reverse (hers are green outer, brown inner).
Wait. That's notable? Mine are similar to the image, but the green band is slightly thinner. Also, I've got quite a few of those little darker-colored specs that are apparently bits of fat or something, but look interesting.
It's called central heterochromia. It's actually a lot more common than people realize (see below -- hazel is heterochromic by definition), but tends to go unnoticed in a lot of cases because the two colors don't have high contrast (ex. olive green/brown). Far more noticeable when it's blue/brown or blue/green.
Fun eye facts: There is no "blue pigment" in human eyes. Blue eyes are in fact unpigmented eyes (or eyes with very low levels of pigment), and the blue color comes from Rayleigh scattering of shortwave frequencies in reflected light (the same effect that causes the sky to be blue).
Grey eyes are similarly unpigmented but have more collagen in the iris, which causes Mie scattering (the same effect that causes a grey sky on overcast or foggy days).
The only pigments in human eyes are melanin (brown/black) and lipochrome (yellow).
Green is a combination of small amounts of melanin and/or lipochrome combined with a moderate amount of Rayleigh scattering. Yellow/brown + blue = green.
Amber is a mixture of melanin and lipochrome (brown + yelllow).
Hazel is essentially heterochromic by definition, as it results when the melanin deposition forms a gradient, causing the melanin/Rayleigh scattering combination of green to transition to higher levels of melanin (and conversely lower levels of scattering and reflection by higher wavelengths) resulting in brown.
EDIT: This is also why most Caucasian babies (especially those of Northern European ancestry) are born with blue eyes initially -- no melanin. The melanocytes develop a few months after birth and begin producing melanin, causing the eyes to change color. Other ethnotypes have higher levels of melanin overall, and thus are typically born with melanin already present in the iris.