I am amazed that decades after the Spectrum was current that clever code has been written to get more colours than previously thought possible in an 8x8 area.
However, none of this was available in the 1980's, when people actually used/played games on these home micros.
The situation was different with the ZX81. Originally this had the lamest display ever, black and white, 40 x 25 characters. Some characters were graphics, i.e. a bit like very blocky unicode. Notionally that was the best you could get. However, you could re-map the characters to RAM and in RAM you could put your own character definitions, e.g. the letter 'A' could be made to be your own 8x8 pixel black and white character. If you re-mapped every character then you could create a rudimentary 'high resolution' game environment. This technique actually required 'shadow RAM' in the 8-16K part of memory. You then had to enter characters the hard way, working out from graph paper what the binary was to be. At the time this was mind blowing. The iphone launch was nothing compared to the excitement of getting high res black and white graphics on the ZX81.
But, it was on the BBC Micro where real mind blowing stuff happened. The game Elite did something utterly crazy with graphics on the BBC B. The top part of the screen was in high res black and white and the lower dashboard/console was in chunkier four colour graphics. The Braben/Bell team had managed to not only think of switching modes mid screen, they implemented it and they did it all with genuine 3D.
This only worked on the BBC Micro, other variants of Elite were not as good as there wasn't the hardware on other systems to do truly cool stuff.
Imagine if you went to a web page and the top part had 4K monochrome video even if you didn't think your computer did 4K with the part below the video at 720p with HDR colours, with there being both modes on screen at once. You would be in awe of that, and this is the best analogy I can think of to think of what Elite did.
Elite was a 1980's game and this hardcore hacking of the display modes was available at the time and not something developed demo-scene style decades later.
Elite defied so many things that should not have been possible. As well as the funky screen modes there were things like the thousands of planets, far too many and far too detailed to fit into RAM. This was tantamount to magic.
I never felt that any of the hacks on the Spectrum had that jaw-dropping awe factor, it is a shame that the subsequent video hacks were not available at the time, in the 1980's.