Is the scratch past the primer? Kinda looks like the bare plastic to me, so if that's the case I think all you can really do is fork over for the touch up pen and try to do the best job you can. At least with the pearl white you might be able to get it to match pretty well. If you do need to use the touch up pen, make sure you really shake it up well, my soul red touch up looks more bronze than anything. This is a link to the drive clean videos in case you want to go totally overboard filling in your scratchhttps://www.youtube.com/watch?v=6xi3xmeO6C4.
If the scratch is only to the primer you can try a product like ScratchX or some other polish/compound to maybe get the scratch to fill in. After that, make sure you wax the mirror.