Searching for I have a 21" 5/8 spiral balance with a yellow tip, which replacement tip color should I use?

Hello. Most likely that is not a yellow tip but a faded white tip that is no longer rated. To know what tip color to pick, weigh the window sash these S600-21 Spiral Balances support. You can then match that exact weight with one of the weight ranges listed alongside each color tip option under the S600-21 product description.