Hiya,
Thank you so much for trying this. It's very kind of you to take the time.
To my eye there is till clearly grey parts on your printout; yes, no where near as obvious as mine.
As mentioned, when printing the graphic as a Jpeg it prints perfectly.
May I ask you to try and save, then print off as a jpeg, and then see the difference. There should be no grey at all. This is a watercolour wash made from blues and greens only.
I would be very interested to hear your thoughts after this test.
This issue also happens when using Affinity Designer. I also tried printing via Illustrator and Photoshop, no problems at all!
Thank you