A dark theme for your long IDA session powered by a colorful pastel pallete. long_night supports IDA 7.3+ out of the box and can be used with older versions through the plugin IDASkins.
Official releases can be found here. To get a version that is in development you can clone this repository and copy the folder called long_night.
To install the theme copy the folder called long_night to one of the following paths:
# IDA 7.3+
C:\Program Files\IDA 7.4\themes\
# IDA <=7.2
C:\Program Files\IDA 7.2\plugins\idaskins\themes\