Why is the femometer opk lighter than the walgreens strip opk

💙💙💗Desiree💗💙💙 • Mommy of 4 blessings 🧑‍🤝‍🧑👧🤰

I shouldn't be ovulating again since I got my first positive opk strip and solid smiley on digital on October 10th . Why is the femometer one darker than the walgreens brand blue one?? The only reason why I took the opks was to see if I could see a line on a pregnancy strip one. Why are the lines so dark???