FOR ELDERS

Am I allowed to wear jewelry or watches?

For safety and security reasons, accessories should be simple and conservative and should not distract others from your message. You may wear one simple ring and an inexpensive, conservative-style watch. Do not wear lapel pins, necklaces, or any kind of bracelet (except those with a medical purpose). Tattoos, nose rings, other body piercings, or toe rings are not acceptable.

https://missionary.lds.org/clothing/elder/faq/?lang=eng#bookmark16

FOR SISTERS

What are the guidelines for jewelry? 

For safety and security reasons, jewelry and all other accessories should be simple and professional. Earrings should not hang longer than approximately one inch below the earlobe. Do not wear more than one earring in each ear. Necklaces and rings should also be simple and conservative.

https://missionary.lds.org/clothing/sister/faq/?lang=eng#bookmark19