What about border ON/OFF boolean toggle?
In GenerateBlocks you can update the Pen.Color to:
FBlocks[Brows, Bcols, Srows, Scols].Pen.Color := clNone;
That would produce that there is no visible difference between the underlaying ScrollBox and the space between those shapes.
Later you can press the new button "Border Color", maybe rename that button to Background Color

Here it is 1.30 AM so time to go to sleep. Getting tired now, as I returned to work (yesterday). See you for now. Thanks for the updates and explanations KodeZwerg.
Have a good rest and whenever you are curious about updates, just ask
