I wonder whether your question arises from the two possible and very different meanings of the term transparent, the literal one being equivalent to invisible (0% Opacity) as in untinted glass without reflexion, and the often used descriptive one being partially see through (less than 100% Opacity) as in a faded appearance in front of something else that shows through faded right behind it.
De document has a red backgroud, part of the document is covered by transparant picture, but transparent red is darker red then the original background