Just to avoid any confusion, you are not asking about Property Box colours but Diagram Box background colours.

The colours you describe are not the default colours, so I suspect somehow you have changed them.

Anyway, those colours are set in the Diagram > Options > Boxes tab.

The Condition called Box Type has tabs below for Root, Ancestor, Descendant, Spouse, etc.

Select each tab in turn and use the Edit Features… button to change the Box Fill colours.

If you have never significantly customised the Boxes tab Conditions then there is a shortcut to restore the defaults.

If the only Conditions are Sex, Box Type and <Default> then use the Presets button bottom right.

The Classic (Box Types) option will restore the default colours, and you can experiment with the other options.

Regards, Mike Tate