Opks and color

I'm cd 11. The color seems to get a little dark on one but then light on the next. I'm so confused. Last month I have a positive cd 13 and 14 so I guess today doesn't really matter. Is this normal? The top 2 are from yesterday and the bottom 3 today. 6am, 10:30, and 4:30pm. I know they aren't positive yet lol