Identifying mouldy beans

Hi,

I was wondering if someone could give me some guides for identifying mouldy beans.

I'm new to chocolate making and recently roasted a new batch of beans I had. AsI was doing a pre-roast scan,maybe 10 beans out of ~500 were a duller/grey shell colour covered in white. The bean still seemed a full, "plump" bean - not withered or shrunk.Is this what mould looks like on a bean? I seemed to have a gut instinct not to use them, but then realised I actually had no idea what a mouldy bean looks like.

Is mould on the shell OK (because it gets removed) or does it indicate something askew with the nib?

Is a small % of mouldy beans OK to use or does it affect taste pretty quickly?

Thanks for any help