I believe the skill-based options are NOT blue (because they are greyed out).
I suspect (I'm not looking at it right now) that the greyed out option is not distinct enough from the normal white text option. So, side by side they are not standing out (because when presented with two white-ish text options, I don't think to consider that the skill one is supposed to be blue.
Ok... I've just gotten an option for three conversation options.
1. Normal.
2. Skill check I don't meet.
3. Skill check I do meet.
So, they are white, grey and blue.
Since you've mentioned it's grey, I can see it. If you hadn't told me it was supposed to be grey, on my monitor I wouldn't have noticed.
Could I suggest another colour? Orange or red perhaps? Red might clash with the black background. You're the designer, I'm sure you'll work out what looks good.
Even a darker shade of grey might work... though then it might be an issue if someone has a darker monitor than mine. For my monitor, the white isn't bright enough to distinguish itself from the grey.