The color wheel and color sliders show wrong color range in sRGB mode. (See the picture.)
Windows 7, Unreal Engine 4.6.1 (64-bit)
Hey Denis -
Thank you for your report. I have added your information to the existing report of this issue, for reference UE-6942. As soon as I have any additional information for you I will post here.
Thank You
Eric Ketchum
One month later. 
The bug isn’t fixed in 4.7.3. Can its priority be a little higher? I think colors are very important for human eyes. How can we set proper colors if Color Picker doesn’t work correctly? There is so many cool features in UE4, but without Color Picker it’s like a car with square wheels.
Is this fixed? I think I still have the same bug…
http://i.imgur.com/3gL5P0Z.jpg
Ok, is not a bug, it’s a “feature” because the PBR, forget it.
Hello -
This particular issue does appear to be fixed in 4.9.0 release. Ivan you are showing emissive colors in your screenshot which will never show correctly on the color wheel, the color wheel is set to use 0 to 1 Linear Color and not the 255 range used in Photoshop’s color picker.
Thank You
Eric Ketchum
Hello Eric,
in UE 4.11 the color wheel and color range still show a different color to the sRGB preview:
It would be the best if there would be an option to display the color wheel and slider in sRBG mode, too. Otherwise I find it very difficult to find and pick the right color.
This is still a thing in 4.20.3
I’m still trying to get my head around it… when I do, I’ll try to remember to come back here and update this post…
In the mean time, here’s another thread that talks about it: