Each colour has a particular meaning.

Red
Stop or prohibition
Stop or prohibition

Blue
General information or service road information
General information or service road information

Green
Indicates traffic movement such as turns which are permitted or directional guidance
Indicates traffic movement such as turns which are permitted or directional guidance

Yellow
General warning danger/caution
General warning danger/caution

Fluorescent yellow-green
School zone and school crosswalk ahead signs
School zone and school crosswalk ahead signs

White
Regulatory
Regulatory

Orange
Construction and maintenance warning
Construction and maintenance warning