The element of colour is very important in advertising, and the Canadian government recognized this. They took full advantage of the ideas certain colours would bring across. For example, in the poster previously posted, the letters spelling "Canada West" are large and bright orange. They stand out and grab the eye, so that someone walking by would take notice of the poster.
The sky in the poster is a nice shade of blue, which indicates warm, mild weather- good for growing crops.
The crops themselves are golden. This would make the viewer think of riches.
All of the colours on this poster are bright, so that the viewer would see Canada West as a prosperous, cheery place (as opposed to a frozen wasteland, as it was earlier reputed to be).
This poster makes full use of colour to promote Canada West.