Why are some region variables in Chrome Dev Tools grayed out (light purple)?

Question

Why are some region variables in Chrome Dev Tools grayed out (light purple)?

Answer 1

It seems that gray variables are not enumerable. When pausing a breakpoint, do greyedOutVariableName.propertyIsEnumerable('propertyName') and it should return false.

Object.prototype.propertyIsEnumerable ()

Thanks to ckocagil for # chromium support on Freenode for this!

Answer 2

I want to indicate that the accepted answer is incorrect.

try

 window.chrome.propertyIsEnumerable('webstore') 

and you get true , but window.chrome.webstore is light purple.

Press the (...) button to call the color dark purple, so there are two reasons for light purple.