Cable wiring

Where can I get some information on how to understand the color wiring scheme for serial and parallel cabling.How to read those schemes, which color wire is for what pin #, any and all info ? I understand that 1 goes to 1 as it shows in a scheme but 1 to 1 what. For example: I need to put together a serial 9 pin end with an 25 pin parallel end with a specific wiring, I’ll use RS232 but what and how do I do that. It’s a tranmission cabling scheme from a PC to a automatic table saw.