settings error: custom colour crashes settings

hi

I recently bought a dell 7577 and it was working alright. I decided to change the desktop background to a custom colour and an error appeared and the place which should have the colour panel was plain white. and after that settings crashed and an error message appeared. please help asap.

the screenshots have been attached.

thanksthis is what appears when i select custom colour. i cant click anything on the dialog box. then settings crashes and error message appears.the error message