Diatary fat can also turn to keotenes and cause the strips to show positive. Deydration can also cause a darker color as the keotenes will be more cencentrated. I wouldn't worry to much about the srips though. Many people loose just fine without any color change.

Have you been on induction for only 3 days, or just testing for 3 days? It can take longer then that to enter ketosis for some when starting this WOE. Also are you sure you are getting a good ratio of fat to carbs and protien? Too many carbs or too much protien could mean your body is still burning gluclose. Diatary fat gets every thing going, and provides calories for energy without raising insulin levels.

It could just be a case of be more patient. If you are losing weight or clothes are starting to fit better, don't stress the strips. They aren't worth it