Cut and paste this URL to share the unmodified register and value:
https://regviz.com/r/stm32/stm32f7/STM32F746/DMA2D/FGPFCCR#0x0
foreground PFC control register
Color mode
CLUT color mode
Start
CLUT size
Alpha mode
Alpha value
https://github.com/modm-io/cmsis-svd-stm32