Camera lens; large speck like dust; gives a slight center color cast on raw images.
(cast is hard to detect or not so obvious; noticeable in the resulting images)
Best ways in removal; so as to restore back original color?
As indicated, an LCC (Lens Cast Calibration) shot will allow to address the issue with the best quality.
When you shoot Raw files, you can also use RawTherapee
to do it automatically for one or many files with the "Flat field" functionality.