It was supposed to be red.
Coincidentally, today in the local museum, which has got a giant exhibition split into "AFRICA", "ASIA", EUROPE", "AUSTRALASIA" and "NORTH AMERICA" which shows cultural artefacts and native animals from those continents there is, in the North American section, a Canadian flag.
The caption next to it says that the first visit by a British royal (the Prince of Wales) to Canada occured in 1860. The intention was to have thousands of people lining the streets, with those of English descent wearing a red rose and those of Scottish descent wearing a thistle in a similar way as the British and people in parts of the Commonwealth wear red poppies in November.
However, the crowd decided that they would wear maple leaves that symbolise Canada (the maple leaf was used to symbolise Canada, or what would later become Canada, as far back as 1700), and so the maple leaf ended up on the Canadian flag - albeit 100 years later.
It was drawn red as that's the colour that the maple leaf changes to in autumn.
The number of points on the leaf has no significance; they do not, for instance, represent the ten provinces plus one point for the territories such as the Australian star denotes. In fact, some of the very first Canadian flags made had maple leaves of variously 13 and 15 points or more. The points of the maple leaf were determined by taking various samples of leaves and putting them in a wind tunnel to see what looks the best
An autumn maple leaf