Soul Stealer Vladimir's ultimate not visible enough

I don't have the best of sight (a bit colorblind, difficulties with certain dark colors), but god if it is frustrating to recognize having a mark on your body when it's just about to proc because you couldn't see his ultimate. Comparing it to a big bright red giant circle which also seems to last more (the visual effect) you can see what I mean, can I have a Rioter opinion plox? @riot