The Kangaroos' backline showed its true colours to run away in the second half from cross-town rivals the Queanbeyan Blues, winning 26-10 at Seiffert Oval.

The Bulls, spurred by a hat-trick of tries from James Ulrick, opened their new ground at Gungahlin Enclosed in style, hammering the West Belconnen Warriors 42-6.

In a typical Queanbeyan derby, it was a tight contest with the Roos leading 8-4 at half-time.

But two tries apiece to fullback Bryan Cronan and Robbie Byatt sealed the deal for the Roos in the second half. Tuggeranong import Josh Mitchell was outstanding at hooker, combining nicely with halves Jordan Macey and Luke Jones.

But Kangaroos coach Aaron Gorrell wasn't thrilled by the victory, although it puts his team behind only Gungahlin on for-and-against.

"A decent side would have been up by 20 points," Gorrell said of the first half. "We had all the ball and all the field position and so we took our foot off their throat and let them back in the game.

"Hopefully if we do that later in the year, we’ll put a side away."

A knock-on from Blues fullback Tom Ruedinger gave the Kangaroos the first scoring opportunity, and opposite number Cronan continued his try-scoring form by diving over in the corner off the next play.

The Kangaroos forwards fired up, despite dropped ball, and centre Robbie Byatt again converted a wide ball movement in the same corner.

The men in maroon were on top, but a beautifully placed Marc Herbert grubber found a pouncing Levi Freeman to have the Blues back in the game at the break.

The Blues took the lead early in the second half when Jake Knight scored, but errors cost them and they became lazy in defence.

"We started slowly and didn’t hang in from there," Blues skipper Herbert said.

"We were still in the match at half-time but conceded too much ball towards the end, which cost us."