the standard colours for CAT5(e) or CAT6 ethernet cable are:
green, green stripe
blue, blue stripe
orange, orang stripe
brown, brown stripe
the typical setup for an ethernet connection in an RJ45 (the crystal end with the connection tab towards you) is
1 green stripe
3 orange stripe
5 blue stripe
7 brown stripe
Wires 1 & 2 are used to transmit data from the PC to the router/modem (TX) and wires 3 & 6 are used to recieve information from the modem/router (RX). in this fasion, information flows along one pair or another and is expected to arrive at that pinout. the router/hub/modem takes care of the transition to the next cable or out to the internet.
In a crossover cable ONE end is configured as above, but the colours for wires 1, 2, 3, and 6 are exchanged so that when no hardware is between the two PCs/components the signal is transmited at wire 1 & 2 and recieved on pins 3 & 6 on the other system/component. the other colours are placed for backward compatibilitiy and other applications, such as power over ethernet.
following the standard above allows anybody familiar with RJ45 connections repair a connection with a standard colour code and pattern without having to see the other end. If you know you need to replace one end of a patch cable, you use the standard termination.