The TL: DR is that Scratch's eyes as seen in the show are the same as Dash's. But here's a wall of text and helpful visual aids to help explain.
Magenta is not red (and it's not really violet either).
For reference, this is Dash's eye pulled right from the official artwork (and ergo how I made my color guide). The eye gradients are always composed of at least two to three colors, and they all go from a darker to brighter luminance. It never goes dark-light-dark, though it can certainly change hue.
I've also included a screengrab of Dash from the show.
The flash assets used in the promo sites are the real deal from Studio B, the web people
