2.1.1266 Part 4 Section 18.104.22.168.19, lum (Luminance)
For additional notes that apply to this portion of the standard, please see the notes for blue, §22.214.171.124.4(a).
a. The standard allows luminance to be specified either as an attribute of a parent element or as a child element.
In Office, using child element lum will override the corresponding value specified in a parent element and may produce unexpected color.