Thank you for sharing those additional details with us, your efforts do not go unnoticed. This will be taken into consideration moving forward with the task.
The RGB value of the cell background needs to be between 155,155,155 and 0,0,0 in order to reproduce this issue.
The result of this problem is that the foreground color of the cell will always be white, regardless of the foreground color that is specified. Affects PDF only.