I never felt the OT’s sound was “grainy.” at least not in an SP1200 sorta way. and I’ve owned both mk variants (never heard a major difference between them, btw). but I guess maybe if you throw the lo-fi effect on everything… 
I think there’s pluses and minuses of both. but ultimately the improved workflow is why I prefer the mk2.
Specifications of both MK1 and 2 are on Elektron site.
As I remember MK2 has a slightly better noise level.
Also power supply is redesigned, probably better.
I don’t think any software performance had been changed.
(Colour as in paint job. )
Which is why s little context will help us, help you. You want something, you gotta share something.
At least you can tell a difference between black and grey. Not so much with OT mk1 and mk2 audio.
One is black. One is grey
I think the only thing that’s different between the MK1 and MK2 is the inputs are a little louder, meaning you don’t have to gain them to get signal. The rest is cosmetic. There are a bunch of long threads on here about the differences between the two. I could search them if you need.
My opinion-They both sound great. There you go.
Here are some other opinions.
MK2 inputs have more headroom? Better at avoiding clipping with hot modular signals? I’ve only used MK1s.
The Black one sounds obviously much better.
Bear in mind in 1872 when the OTmk1 was announced the quality of MP3 compression was far inferior hence the gritty sound. 
The soldering tin used on the MK1 units had small traces of precious metals due to a metallurgic anomaly Elektron has yet to reproduce and thus the sound inside travels a bit faster and thus the unit has lower latency.
I like this one. Love my MK1.
What I can hear is, that the inputs on mkii are slightly louder. But nothing different enough in audio input or output that it should matter. Lots of other more important differences (oled vs larger screen, build, encoders, design, shortcut buttons, button shape, quality of parts, size with I/O ports, etc.).
Is there something wrong with the build, design or quality of parts on the MK1?
Mki is IMO build better than mkii. But Elektron states, that the longevity of the parts used in mkii is better. Designwise, there are a few threads pointing out the placement of the buttons on the mkii as being poor design - but one of the trades they had to make, with the redesigned button shape.
ah, right. totally agree, i love the mk1 box design while digitakt and mk2 leave me quite cold
