Here's a quick fix for that!
***Go to Dashboard >> Account Settings >> Google+ ...then scroll down to "Photos" and UNCHECK the Auto Enhance option. ***
As you can tell, my blog is still under construction. And one of the problems I've encountered while pimping up my page is when uploading my image header and not being able to blend in with my page background. I used Photoshop first to create my header and each time I upload it on my blog, a grayish color shows up that is very noticeable. I tried for the second time to edit my image header on picmonkey and still the outcome is the same. It is annoying to look at and I can't leave it just like that. Though I haven't tried using other photo storage websites, I was determined to get to the bottom of this. Only to find out that the culprit is Auto Enhance.
Hope you find this helpful and goodluck! xox