Which metal works best with yellow sapphire, for a finger ring?

Yellow sapphire could look good in silver if it is of the lighter variety - a richer yellow would normally look better in gold though.

Silver is still a precious metal and will last a lifetime, but yes, it does tarnish - this is due to the copper content in the sterling silver which also makes it hard and durable.

The yellow-orange colour does sound like tarnish, it is possible that the silver is reacting to your skin (totally normal, but it happens at different speeds with different people), so you're best to get a silver polishing cloth from the jeweller's and give it a good rub over with that. These cloths have polishing compounds impregnated in the fabric and it will make it shiny again.

To clean around the stone after polishing with the cloth, get a small bowl of lukewarm water, add a couple of drops of mild liquid detergent and soak the ring for a couple of minutes, then get an old soft toothbrush and scrub around the setting. Rinse in clean water and leave on a paper towel to dry.

As it has tarnished so quickly, to prevent the tarnish building up and becoming hard to remove, I would recommend that you clean it regularly - after each wear if it's a special occasion ring or every couple of days if its worn all the time. If you don't wear it for a while, keep it in a airtight environment - eg. a ziplock bag - to keep the air out.

Is your ring plated, by any chance? The yellow-orange color usually indicates silver plating which is wearing thin.

Clean it first by washing it or using a gentle silver polish, then buff it with a polishing cloth. If it is still yellowish in color, you probably purchased a silver plated ring setting. Since it has only been a week, try taking it back to the store. It should take much longer for silver plating to wear off, unless your skin is very acidic.

If your skin has a higher acid content, you will not be able to wear silver plated jewelry without that happening quite quickly.

normaly, the semi-gemstone like yellow sapphire can be set in silver due to the value of stone, because it is cheaper comapring to diamonds and ruby;

you could choose white gold, but that is going to be cost;

u said your ring is turning slightly yellow-orange in color, that is not because of the metal, it can be : there is some dust or dirty things on the stone, so the color is changing due to the reflection! it is normal. u could clean it, then it is going to be shining!

good luck!