[Ellie May]

Black parts next to the pink is normal pigment.

They are all different. If you can get most of the stuff off by brushing alone, then they are probably fine. The teeth should be checked preferably twice yearly by the vet to assess whether or not a dental is needed. Very generally, dentals are needed every 6 months to 2 years (some Yorkies without home care could use a dental every 3 months and Ellie hasn't needed one for 3 years, so this varies). Because it averages to about yearly, that is the general recommendation.

A little bit of brown on the teeth may not indicate that a dental is needed whereas almost perfect teeth doesn't necessarily indicate that a dental can be skipped (because the gums needs to be assessed). So only a vet can look and answer this.