Ricoh Aficio 250 Copier "oki fault replace image drum" Questions

...OKI (magenta). Now it appears that registration is completely off. When printing an image, there is a band of yellow at the top about 6mm high, and a band of purple (not cyan) at the bottom about 6mm ...

...fault find, fix is possible toner more than likely drum/drums, do a print of each colour and change drums as indicated by failure in its colour to print, check transport belt is OK and led heads are ...