(I have never worked out which splash screen is which.)
On a separate installation of Cauldron, for a while there was no splash screen after selecting Mageia and while it was loading, only a grey screen with 3x "?". That cured itself with time.
I have just upgraded my working Official to Mga 6. To begin with, the Grub2 menu was in a white font on a black background. Running an "update" from my installation media fixed that, but the grey bootup screen has returned. I can probably wait until the next update of the graphics, but is there any fix I can apply now?