Bright light is great for cacti that are accustomed to bright light. Not so much for those that are not. Red is an indicator of stress. If it's just a mild blush, I might leave it be, to get used to its new environment. Else I might tone it down a bit for the time being.

As GermanStar said, it might be a sign of stress.

I found one site that says Disocactus ramulosus turns red in high light. See link below.

A new shoot on my Epiphyllum is all bright red...but it is definitely stressed. :P

Here is a link that might be useful: Disocactus ramulosus