Aloha F,
After looking in, C6.5 ‘Preferences’.
(in the middle) ‘Edit Windows’ section,
‘Horizontal Grid Intensity’ IS working here in C6.5.
However in the top ‘Project Window’ section,
it seems the ‘Work Area Brightness’
has to be set fairly ‘brite’ to see any real effect or change.
Good Luck!
{‘-’}