One more pic, in colour even. Source:
canadiansoldiers.com.
Markings and unit, according to John McGillivray:
-Division sign (yellow maple leaf on a blue background) indicates that it belongs to the 2nd Canadian Infantry Division.
-The red over blue AoS with the number 42 - 4th Field Regiment Royal Canadian Artillery
- Tac Sign - the blue square with the bottom left (viewers right) corner in red - the second battery of the Regiment - 14th Field Battery.