Everyone’s skin is different and therefore reacts differently. The colour does look a touch off for now, but it’s hard to know how it will settle. That’s why I reckon you’re best off ringing them and discussing it before your next session. There’s only so much that us blokes on the forum can say as we’re not the experts and don’t really know enough about it all. I’d get in touch with Skalp mate, send them some photos of how it’s looking and chat with them. That’s how you’ll get the best idea of what’s needed.
Nothing to worry about, as td01 has said everyone’s skin is different, you might just have slightly more sensitive skin so it will take longer to settle down, once you have had the 3rd session and it’s really settled down it will look great, just be patient mate