This is a sample of how orange shift affects black ink. Both images were printed at the same time, on the same piece of Epson Premium Glossy Photo Paper, using black ink only. The right hand image is the dark stored control. The left image was exposed to my "UV" test. The ink on the tested sample is clearly brown compared to the control sample

You can see a microscope image of this black ink gray scale here. This image clearly shows that only black ink was used, and that it has turned brown.

Again, note that my scanner doesn't seem to handle orange/brown colors very well. The sample exposed in the ozone chamber actually looks about like this scanner output looks. The color shift on the UV sample is much more brown than this image shows.