Akro, they're coverage diagrams based on terrain and antenna propagation, so to that extent they're theoretical. They don't account for things like atmospheric conditions on the day and localised anomalies.
The colours around the J-curve, Perth and Darwin represents radar coverage. The other colours are for ADS-B and TASWAM. No idea why different colours were used for the different altitudes, but there is no significance in it.
They're not produced to try and fool you or anyone. They're exactly the same as we in ATC get to see and what you'd expect from line-of-sight radio propagation.
The atmosphere can do weird and wonderful things to RF propagation at times - we'll get as big hole in radar coverage at say F390 but see aircraft at F330 no problems. Not to mention ducting and skipping of VHF radio