Purple footed fern frond
Today I was taking a look at my footed fern, and noticed one of the newer fronds is a dark purple color. I'm not sure if it started out this way because, to be honest, I hadn't taken a close look at it within the last few days, and it does put up new fronds quite often.
Some of the newer fronds start off reddish or darker sometimes, but the leaves always end up green. This one, however, was all purple, like I said. The leaf looks healthy otherwise and nothing has changed recently in its environment (near a window but not full sun, maybe a couple hours of sun in the morning).
I'm new to this type of plant, and have had it a few months. Does this sort of thing happen sometimes? Why the color change on just this one frond?