I don't know about any clear lithium grease, but do know that the black in most gear train grease over time is actually particulate matter (wear particles and dust and dirt) that accumulates over time. I have unused white lithium grease that is nearly five decades old and it has had very little color change over time. Originally white is is now an dark ivory color.
Perhaps a filter or other means of keeping outside particles away from your gear train would help.