Here you would put the background colour that you want your journal to have in.
To do that, just use the #xxxxxx format code for the colours - in case you don't know the code for your colour, go to one of these sites:
(Colour Picker 1) (2), chose the colour you want to use, and put the #xxxxxx code found in the middle of the tool into the appropriate fields here.
You can use this tool on all the other #xxxxxx codes you need here, too ^-^
(Note: Make sure you enter the colours with the leading # sign. Just entering 183270 (for example) won't work, whereas #183270 will.)