2.1.1281 Part 1 Section 188.8.131.52, clrChange (Color Change Effect)
a. The standard states that attribute useA specifies whether alpha values are considered for the effect.
In Office, if the value of useA is true, alpha is considered for finding a match for clrFrom, and the alpha is replaced with the alpha value in clrTo. If useA is false, no alpha values are changed.