FontFadedBug.zip (7.4 MB)
Included in the ZIP is a PPTX and the resulting PDF. The grey font is extremely faded when converted by Aspose. Tried the latest Aspose NuGets as well.
I have worked with the presentation file shared by you and have been able to observe the issue specified. An issue with ID SLIDESNET-40181 has been created in our issue tracking system to further investigate and resolve the issue. This thread has been linked with the issue so that you may be automatically notified once the issue will be fixed.