Physics vs. graphics
Computer graphics terms are somewhat confusing and disagree with physics:
Graphics: color of an object; physics: reflection spectrum (i.e. fraction of light of each frequency that gets reflected).
Graphics: intensity or color of a light ray; physics: radiance distribution (measured in watts/steradian/meter2/meter)
Graphics: intensity or color of a point light source; physics: intensity spectrum of a point light source (almost in agreement!) measured in watts/steradian/meter.