Is there any known, or conceivable technology, that would improve the color field for displays?

Adding color channels can help. For example, Sharp sells LCD televisions with an extra yellow channel. Problem is that these need software computes/approximates/guesses at the perceived yellowness of pixels based on their RGB (for computer monitors) or HSV? (for television) values. I have no idea how well we know color perception to pull that of reliably, whether it actually can work across the population (including the colorblind), or whether they implemented the best-known solution.

There are "HDR" displays that can display a wider range of colours, my university had one.

HDR (high dynamic range) displays are those that can reproduce wider differences between dark and light. What you're talking about would be called a wide gamut display, such as an LCD with RGB LED backlighting or a special wide-gamut fluorescent backlight.