Gary Caldwell is a British comics artist and colourist who, along with artist Neil Googe, co-created the characters of Sam, Simon, Clive and Rufus (see picture) in the 2000 AD strip Survival Geeks, and the character of Junko Asahara in Hondo-City Justice. He has worked for 2000 AD (on strips including Nikolai Dante and Sinister Dexter), the Judge Dredd Megazine, Doctor Who: The Eleventh Doctor and Strip (colouring reprints of Hook Jaw). Caldwell has also inked strips such as Judge Dredd and coloured Lilly Mackenzie and the Mines of Charybdis.
Gary Caldwell's website is here and his Twitter feed is here.