How do we know that? Well, we've scientifically measured the new One's display, and found out that its saturated colors extend beyond the boundaries of the standard sRGB colorspace. What this means is that with the new One, HTC is saying 'enough!' to that whole true-to-life game, and is instead going for a more visually-striking, yet slightly more unrealistic approach. Measuring the color gamut of the HTC One (M8), we've found out that its area extends to 110% of the standard sRGB gamut.
Comparing this number to the color gamuts of other popular phones with quality LCD screens out there, it appears that none has yet attempted to reach such level of color saturation. Now, keep in mind that having a larger color gamut doesn't translate into better or more accurate colors. Since most content on the web is optimized for the sRGB colorspace (so that it appears the same on all machines), having a display with larger color gamut (more saturated colors) means that this display may look fancy, but also off target.
When it comes to color gamut, there really isn't right or wrong approach. It's all about what we, as users, value more: pumped-up visuals, or accurate visuals. With this new screen with 110% of standard color gamut, HTC is moving slightly towards the former, although it remains way more accurate than the AMOLED displays used by Samsung and Nokia.
So, to put the new One's 110% color gamut in some perspective, we can point out that last year's HTC One and the LG G2 both have 100% color gamut areas (compared to sRGB size), while the Nexus 5 and iPhone 5s have 98% and 97%, respectively. You should also keep in mind that two phones with 100% color gamut size may display significantly different colors! What this number indicates is solely how much of a color range a screen can display - it doesn't necessarily mean that this color range will overlap with the sRGB color range.