If using any of the pubs near the stations buses to the stadium are from Bruff Close which is to the north of Colchester Main Line station, shown on the map below.
As far as we are aware there are no alcohol provisions for away fans at the stadium. 
The Norfolk: Recently refurbished. About 300 yards from Colchester North station, going towards the town centre and away from the stadium. Advantage is it accepts away fans. Disadvantage - Greene King ales are pretty poor these days. Does IPA, Abbot and Old Speckled Hen as its real ales. There's a pool table and Sky Sports on a big screen. 132-134 North Station Road.
Bottom square south of station; North Station Road and the Norfolk.
Top square north of station; Bergholt Road and the Bricklayers.
Top square first right off the roundabout; The buses to the stadium in Bruff Close.
The Bricklayers: Nearer to the station than the Norfolk and a better pub but it states it's for home fans only so doubtful your get in with colours. Serves Adnams beers, including a guest or two and a traditional cider. Food is home cooked and good value. There's a pool table in the public bar. 27, Bergholt Road.
Going into Town
You could stay on the train from Colchester (North) mainline station to Colchester Town, a 7 minute journey and tickets are still valid, where there are plenty of pubs to be found but you are going even further away from the ground.
St John's Street will find the CAMRA listed pub, the Fox & Fiddle, which serves a number of real ales.
Almost next door is the Playhouse, which is a Wetherspoons outlet. This former theatre is a spectacular setting for a bar, as the original dress circle and stage of the theatre have been preserved and is well worth a visit.
Give yourself enough time to jump back on a train to the main line station and the bus at Bruff Close. There's a 13.28 and a 13.45 which will get you to ground in time, the 14.15 could be pushing it!
The Fox and Fiddle: Nice enough pub with 6 ales on hand pump. The home cooked food is particularly good. St. John Street.
The Fox & Fiddle is left hand box top of Butt Road by the Parking, the Weatherspoon Playhouse is next door at No.4.
Nearest the ground
The Dog and Pheasant: Three quarters of a mile away from the stadium but officially for home fans only, so no colours. It has got some decent beers at a fair price, usually Green King and Abbott, and as a Hungry Horse the food is basic but cheap.
Nayland Road and the pub to the left, the ground to the top of Nayland Rd. and to the right.