Safe Mode loads a minimum of Drivers
to start Windows in that Safe Mode.
Compare it to a racehorse galloping, to a quarterhorse plodding along, but getrting some work done
Windows loads the basic Graphics Drivers to allow it to run, not the Onboard Graphics or Graphics Card Drivers that would run in Normal Mode and which you obtain from the Manufacturer.
To fix your problem:
go to either your Computer or Graphics Card Manufacturer's website > look for a Drivers and Download Section > look for your Computer or Graphics Card Model Number > your Operating System > Drivers for it: either Video / Graphics / Chipset (depending on wording there) > download and install the Drivers.
If that does not fix it, it would then appear to be a Graphics Hardware problem.
If a Desktop, either swap your Graphics Card with a good one.
Or if Onboard Graphics , you will have to install a Graphics Card in a slot in the Motherboard to see if that fixes the problem.
If a Laptop; if under Warranty, contact the Manufacturer.
If not under Warranty, contact a good, local Repair Shop.