In an assembly, it can be quite useful to have different parts shown in different colours. Whether that be to differentiate between parts, to display final colour or to indicate whether a part has been purchased or not.
This is easy in an assembly, but when you come to a drawing, the Hidden Lines Visible (HLV) and Hidden Lines Removed (HLR) display modes remove this colour, showing all the lines in black. You can modify this behaviour by going to; System Options > document properties tab > select detailing from the list on the left > find “Use model color for HLR/HLV in drawings” from the list on the right.
By Jon Weston-Stanley