I have 2 front crowns and not happy they don't match other teeth. Dentist says the only way to achieve that is to do all six?

Hi:For more accurate advice please post a photo of your smile.  Generally depending on the color of your natural teeth, it is difficult to do only 2 front crown, however, an experienced cosmetic dentist working with a master technician will be able to match the adjacent teeth.  In my practice I often have to do 1 or 2 front crowns that has to match the natural teeth.Best,Dr. Maddahi

Can you upload a picture?  Depending on the situation, matching the teeth can be extremely difficult.  The dental technicians that make the crowns vary in their skills.  In order to get a perfect shade match, your dentist may need to use a different technician or lab to get the results that you desire.  Also, to get the best match,  the highly skilled dental technicians charge a premium.  Often, the patient will pay additional lab fees for a perfect match. Enamel is translucent and reflects and refracts the light. Dental porcelain is not translucent.
To answer your question, doing 4 or 6 teeth will be easier for the less skilled technicians to match.  If I were you, instead of doing more crowns or veneers, pay more for a better lab technician.