These are Ethernet cables.
These are Ethernet cables.
They probably came from the motherboard and power supply unit.
First image (purple): seems to be an adapter cable, type uncertain, photo not very sharp. Resembles a Dupont connector. Often found in Arduino and Raspberry projects. Currently, using PC cases is rare—usually placed on the motherboard for front I/O. Second image (black red): likely a 2 or 3-pin Molex adapter cable. None of these connectors fit into a PSU, probably not used today.