When I have sirloin steaks, I take them out of the fridge and season them while they return to room temperature before I cook them.

I add various seasonings - salt, pepper, garlic etc. it depends on my mood.

I notice that after I season them, the more heavily seasoned areas turn grey. Why is this? Is it to do with dehydration from salt or something else?

The steaks are always delicious so it's not a concern, I'm just curious as to what causes the colour change.