A pocket magnifying glass and small pocket lght can help as well as looking at the board diagram if no color coded areas are seen on the block of small pins. The diagram will show what pin is negative or positive while a close look at the ends of the wires themselves will usually see the + plus or -minus sign regardless of whether the pair is red and black, white and green, white and black printed on them right about where the small plug is on the ends.
But pin for wire verification is by first hand examination and review on the manual's diagram for this. For anyone working on a system they have to get right in there and look to verify things. Each make and style case will often use different color combinations on the wiring depending on what is seen on the front or top like usb ports and audio jacks even E_Sata type ports along with the power, reset, and led lights.