Samsung printer only prints grayscale

I'm on Mint 18.3 and I cannot print in colors on a CLP-680ND. The same happened with 18.2 and 18.1 as far as I can remember, but a previous one used to work, maybe 17.x or even 16.x.

Whenever I print from whatever program and from printer manager (test page), the print is executed in grayscale. Every color setting is of course enabled. The eco-settings are disabled on the printer panel.

I tried with LPD via DNS-SD, AppSocket, ipp. I'm using the latest (and only, and automatically found by Mint) ppd file from Samsung.

If I boot an Ubuntu 17.04 live, the printer is automatically installed (via ipp) and the test page is correctly printed with colors. The same procedure with Mint prints grayscale. Windows, smartphones and direct print via Samsung web interface are ok.

Any clue?