Here's the International Orienteering Federation's manual for control description symbols: [Link]
Here's an online interactive quiz for learning & reviewing the IOF control description symbols: [Link]
Here's the IOF manual for map colors & symbols. In particular, see Section 4 starting on page 5: [Link]
One fundamental principle for map colors is as follows:
White represents runnable forest. (As opposed to USGS topo maps, where forest is depicted as green.)
Yellow represents open, easily runnable areas, such as a clearing. Yellow terrain can be divided into several sub-categories based on relative runnability -- lighter yellow, hatched yellow, etc.
Green represents denser forest and undergrowth, and can be shaded according to runnability (light green to dark green, hatched green, etc.). You usually wouldn't want to fight your way through thick underbrush denoted as dark green.
All of these reference items are available on the RMOC website. Click "Links & Resources" in the left-hand navigation bar, and then click into the category called "Orienteering Websites".