Green, blue, red and black are the known colours to indicate the difficulty of a ski slope in Europe. In North America it is green (corresponds to European blue), blue (red), black diamond (black) and double black diamond (no equivalent). Double black diamond slopes are usually steep, difficult couloirs (chutes) outside the groomed slopes. As opposed to Europe, where everything outside the marked slopes is considered “off boundary”, in Canada a ski resort is an area, which, independent whether a slope is groomed or not, is controlled and safety-checked by the ski patrol.
Most ski resorts I know have their fair share of (European) blue and red slopes, but struggle to offer decent black ones. Not so Revelstoke. The problem here is missing (European) blue and red slopes!
The right picture shows me having done two turns into “Follow Me”, a slope marked as blue. The picture on top shows me shortly before my second turn into “Follow Me”: