So, the standard for color nowadays is 8 bits per channel - red, green, and blue - for 24 bits total (plus another 8 for alpha channel, but that isn't relevant here).
Most TN panels are 6 bit. This essentially means that the last two bits are lost, so fine color detail is lost. Modern TN panels sometimes have "FRC", or "temporal dithering", that tries to flicker the image between two values to recover the last two bits of information (as the display has the info, it just isn't able to use it normally).
Conversely, most IPS panels are 8 bit, and some are 10 bit (note that if you don't have 10-bit content, 10-bit panels' extra capability is wasted.
Also, why looking at a TN panel from below helps with viewing this: TN panels suffer from severe color shift when looking at them not straight on. There's films that can be, and are, applied to improve viewing angles, but it typically works best to optimize for left, right, and looking at the panel from above (at least for PC monitors), with no improvement for looking at the panel from below. (Note that some panels are used in a way that you optimize looking at them from below, so looking at it from above would cause the same effect.) That severe color shift is what's revealing the background.