Electrical schematics are simply drawings that use standard symbols to represent various pieces of equipment such as power isolators, circuit breakers, fuses, relays, contactors, motors etc, which are joined up using lines to represent the wires that connect the bits together. There are a lot of industry standard symbols and rules for the interconnection of equipment, and for earth connections, emergency stop circuits etc. In order to understand and interpret circuit schematics and equipment wiring diagrams, you must first study and learn the common symbols and wiring rules. There are ISO standard symbols (International Standards Organisation), and these can be found in any manufacturer's catalogue for common control equipment. (Siemens, Telemecanique, Allen Bradley etc)
There are also industry standard colurs for the wiring for different voltages, i.e. 3 phase ac, single phase 110 volts ac control voltage, 24 volts dc control etc. Standards vary between Europe and USA, but if you know one set you will be able to interpret the rest fairly easily. There is no magic wand, you have to study and learn. Most electrical drawing software packages (Autocad etc)have built in symbols for all the common types of equipment. Some drawing packages use different coloured lines for different voltage wiring, but the colours in the drawing do not reflect the colour of the wire that is actually used in the system wiring. Standards and practices have changed over the years, and a circuit drawing done by hand on a drawing board 30 years ago will be completely different from modern practices. There is no substitute for experience when faced with such old drawings, and you might need and old guy like me to help with old stuff.
I wish you luck -I don't have to worry about it any more, as I have just retired from 45 years in electrical engineering!