The graphs are three representations of the same data. The 'Average' graph shows the lowest, highest, current, and average signal level seen at each sampled frequency since you started the scan. The 'Statistics' graph simply plots a single pixel marking signal level at each frequency, then adds more pixels on subsequent scan cycles, so that eventually they build up to what you see.
Both of these can be generally read as "higher on the graph is higher signal is worse interference". The 'Statistics' graph uses color to reflect repeated results - IE, if you see -74.1dB at a given frequency every single time, the pixel representing that sample will start dark blue (see color-code key at top right of graph) then get paler blue, greener, yellower, redder as more samples draw on the same pixel.
The third graph, 'Spectrogram', draws one horizontal line for each scan across the spectrum, and represents the signal level by color. Over time it builds up a visualization of about the past 8 minutes worth of samples, with the most recent at the bottom. This one lets you readily see intermittent interference, and is sometimes helpful if you're running a SA at the same time you're turning off radios on nearby towers to try to find an interference source. (though it's worth noting that an AP running with GPS sync WILL show up as an interfering signal but if all radios are configured correctly SHOULD NOT actually interfere with another GPS synced AP)
Now if you're looking at the attached graphs trying to find your best-choice channel, it depends also on what the use is (point to point vs point to multipoint) and channel width you require. For example you have a pretty inviting spot for a 20-MHz wide channel centered on 5845 where the noise floor appears to be around -85dB to -90dB, but if you require 40MHz that would overlap interfering signals to either side that appear to be 10-15dB stronger than the interference from 5835 to 5855 - might be perfectly workable (PtP at -55dB for instance) or might prove unworkable (PtMP with some clients in the mid-high -70s) depending on the situation.
I don't know what regulatory limitations apply to you, so I can't advise on what channels are 'good' or 'bad' per these graphs, but it's necessary to consider the max transmit power and max EIRP limitations in some regions at various frequencies as well as what interfering signals you see. (In US/FCC, for example, -75 interference might be easily overcome at 5815MHz with the allowed 23dB max transmit power, while the same interference level at 5315MHz might be impossible to overcome with the 13dB transmit power limit)
So to summarize, closer to the bottom on the graph image means lower inteference for the first two graphs, while dark green/blue/black means lower interference on the third graph and the 'bottom' of the third graph is the most recent scan. (and yes, red color means high interference)