The HP Prime is an excellent machine, no dice! However, I could not embrace it fully yet, the same way I did with the 28 and the 48 family. I think that the root causes of this distance are the lack of RPL in CAS (although you can still use RPL for numerical computations), and the oddball programming language. This is why I take my time before refreshing my primes. The three models I own today have the HW version A (2013), version C (2014) and version C (2016). I will not get into the main differences, you can find them easily on the web, but rather touch on the improved color scheme used for the keyboard. Gene Wright’s HHC 2004 talk about Calculating Contrast gives a method to evaluate color contrasts used for calculator keyboards by computing the distances in a 3D RGB space. I did a couple of screenshots but I encourage you to look-up this interesting talk. It seems that HP listened to their users complains about the low readability of the keyboard, incriminating the pick of the light blue and orange colors. The latest spin of the Prime has a darker color scheme that improves the readability of the keyboard. Note that the upper part of the keyboard (in the black section of the calculator), uses the original light blue color, which is a good thing. But I still miss my RPL in the CAS and the programming language…