We test materials for potential staining by having our girls n boys wear prototypes for a few weeks. If they stain then we try another material in the same color or we avoid that color all together.
For our jeans however, there is no decent looking replacement material that looks and feels like denim. However, we wash our jeans a few times before shipping and recommend that folks wash them a few times after they get them too. As a result, our jeans are less prone to staining when worn for short periods (a few days) - also, our soft vinyl is a mix that is more resilient (but not immune) against staining.
Jeans worn for longer than a few days could stain so I came up with a series of stain prevention shorts and leggings. Stain prevention shorts or leggings only work if their length is longer than the jeans being worn which means that it must show over the top of the jeans which would look...quite bad. To overcome this issue, I put some lace at the top which not only fulfills the purpose but looks kinda cute too.
If you are buying the tights then remove the feet first and pull the bottom of the tights through the bottom of the jeans.
While these stain prevention goodies will do their job, they will also restrict movement a wee bit as the jeans are a tight fit already.