Old U's forward on new U's forward.
That's the verdict from former U's centre forward Mark Sale, who is now First Team Coach at Birmingham City, from whom the U's bought Johnstone.
"Denny is a great character, works extremely hard and just gets on with the job."
"He's a good size so decent in the air but will also be happy to get in behind and cause problems for opposition defences that way.
"Having had a decent time up at Greenock Morton last season, I'm sure he'll score goals for the U's as they look to get back up to League One."
Sale was at the U's when they won promotion from the fourth tier back in 1998 and hopes that Denny enjoys north Essex and the club.
"I had a fantastic time at Colchester United, a period I'll never forget, and we had a great group of lads that worked hard for the success we got."
"Denny certainly has the work ethic and the quality to be successful with the U's and I wish him and the club well.
"Hopefully, he'll enjoy life in Essex like I did and he'll be part of another U's side being promoted come May next year."