Does this need the photoshop tag? I changed the colors fairly noticeably.
No. Fixing a scan (including adjusting the contrast, saturation, brightness, etc.) does not warrant a photoshop tag. These types of edits are done in an attempt to regain the quatity/accuracy of the original image. With a scan, you only really use the potoshop tag if you extend the image adding new content or modify the image to have it differ from the original.