A color space is like a language for computer monitors. If two monitors are not speaking the same "language" then there will be a miscommunication.
miscommunication on a computer display manifests as shifts in color
accuracy; what I "speak" as "blue" may be heard on your monitor as a
blue with a yellow hue. For everyone to see the same colors, everyone
has to be using the same color space.
The default color
space for the internet is sRBG. PCs automatically use this space. Macs,
however, use Color LCD. Why Apple uses a color space that is not used
by most of the internet is beyond me. But we can fix that.
To properly view photos on the internet, you have to change the default Mac color space.
Please go to System Preferences => Display => Color => sRBG