Thanks guys, I really don't know what you're talking about (Edd)
SDSS sees in five colours (u,g,r,i and z) and computer monitors only do red, green and blue. The usual images make g blue, r green and i blue, but I switched some round to see the u and z instead, making u blue, i green and z red. The weird thing about this object is that the detection was pretty much only in the g band, rendered blue in your original image, but I thought there might be more hints in the others - and I think you can see a faint blue triangle there.
So I suspect it's real, but I don't really have a good idea what it actually is.