Does too much coffee affects strength and color of teeth?

No and yes: No, the coffee itself doesn't affect the strength of the teeth. The amount of sugar and cream you put in the coffee will. Yes, coffee will affect the color of the teeth but not permanently. The stain can be difficult to remove.

Coffee stains teeth: Coffee does not weaken your teeth. Coffee will stain the teeth. See your dentist regularly. Brush and floss daily.

No and staining: Drinking coffee does not adversely affect teeth in any way. Heavy coffee & tea drinkers usually develop heavy surface staining on their teeth. However, this is only surface staining & does not affect the internal color of teeth. The better you brush & floss, the less the teeth will stain. It might also stain fillings especially the older type. Most of this staining can be removed by your dentist.