According to one girl name Erica Griffin (you can google her up. her reviews and explanations on details are really based on her on research and measrements and not from internet available information)
Right, according to her, AMOLED actually has more accurate colour gamut compared to IPS screen
What happened in previous Galaxy phones was that Samsung had deliberately oversaturated the colours. So when people say Galaxy S3 is oversaturated, they're right, but it's not AMOLED's fault, it's the software's fault.
But since Galaxy S4, Samsung had leave the colour meters "more natural" on the colour gamut, according to the results of the colour meter measurements done by her.
Now, on the LCD, the colour gamut is actually narrower than the colour gamut on AMOLED (the wider the colour gamut, the more accurate the colour is according to true colours that human eyes can see). If LCD on natural colour meter mode were to put side by side to AMOLED, it will look as if LCD is undersaturated.
So what most manufacturers do was, they try to emulate AMOLED screen by oversaturating the colours! This is done by deliberately adjusting the colour meters to a more saturated ones (LG G2 according to her colour meter measurements), or by deliberately adjusting the gamma output put make it more saturated (HTC One and Z Ultra). Oversaturating means no more accurate colours, because at some more you will see too dark, and some part you will see too bright compared to the original colour.
So actually what we consumers see as "Good Colour Quality" is actually over saturation of colours, except Galaxy S4 and Note 3 and perhaps newer Galaxy series. Manufacturers found out we actually like oversaturated colours. We can say we like more natural colours but the moment we like what Triluminus or HTC One display, that's actually over saturated colours.
But the downside of AMOLED is that it's not suitable for heavy users, as the screen will degrade overtime due to how the sub pixel works and it's not preventable, according to her.