In Plan a Pregnancy, the fertile window is presented in a scale of red colors, where the most fertile day has the darkest shade of red, and the lightest red color indicates 'fertility unlikely.' (See picture below to see the scale of colors in the Calendar / Month view.)
The brown days are days where more data is needed for the algorithm to be able to exclude or confirm fertility. Brown days mean that you need to keep measuring for the coming days, so there is no need to worry. Non-fertile days are presented in a light green color.
On the Month tab, you see a monthly prediction of your coming cycle; this can range from 1-5 cycles based on your cycle regularity. Remember that future days in the monthly tab are a forecast based on your historical data and are subject to change, so make sure you always check the 'Today' view to see your daily fertility status.
You will also be able to see LH, period, ovulation, and pregnancy tests icons in 'Today', but also when you log intercourse and spotting, which is something that only appears in the 'Today' view.
The graph view is useful to get an overview of your temperature data, and you will also see how the red color changes according to your fertility.
Please refer to the image below to identify the different Natural Cycles icons: