Ethernet Wiring (8P8C, often incorrectly called RJ45)

For a normal cable you can use either T568A or T568B as long as you use the same scheme on both ends. For a cross-over cable use one of each.
# COLOR 1 White/Green 2 Green 3 White/Orange 4 Blue 5 White/Blue 6 Orange 7 White-Brown 8 Brown	EIA/TIA 568A Color Scheme	EIA/TIA 568B Color Scheme

POTS (Plain Old Telephone Service) RJ11, RJ14, RJ25

Holding the connector in your hand tab side down with the cable opening toward you, the pins are numbered 1-6, left to right.

position	RJ25 pin	RJ14 pin	RJ11 pin	Pair	T/R	Cat 5e/6 colors	Old colors
1	1			3	T+	white/green	orange
2	2	1		2	T+	white/orange	black
3	3	2	1	1	R-	blue	red
4	4	3	2	1	T+	white/blue	green
5	5	4		2	R-	orange	yellow
6	6			3	R-	green	blue

While the old solid color code was well established for pairs 1 and 2, there are several conflicting conventions for pair 3. The colors shown above were taken from a vendor of "silver satin" flat 8-conductor phone cable that claims to be standard. Other 6 pair solid (old) bellwire cables may substitute white for orange. At least one other vendor of flat 8-conductor cable uses the sequence blue, orange, black, red, green, yellow, brown and white/slate.

In modern structured wiring Cat5e or Cat6 is commonly used in homes and buildings. The Cat 5e and Cat 6 data lines are often used for both voice or data. The color codes above are the standard and defined within wiring guides.

http://en.wikipedia.org/wiki/RJ11