Black and White Background is turning blue when exporting

[vibe4business]

I've been preparing the final photos for a corporate client where I have a headshot in full color and a separate photo background as black and white. Inside Photoshop it looks perfectly fine, exactly how I want it. But when I go and Export to a PNG or JPG it the background turns a bluish color. What am I doing wrong?

[Peru Bob]

What is the color profile?

[c.pfaffenbichler]

Please post meaningful screenshots.

What are the RGB values of the darkest region and a medium area in the background?