Since I am a newbie. I have only printed 2 svg files that I created. I have never downloaded a pattern, I can only relate to what I know. I have printed my own created svg. But only black lines on white paper. No grey fills on red line. But this topic showed me to try to tweak my svg files to suit my eyes.
I am playing with inkscape for the first time this weekend. I'm creating a file from my own sketch. Now I will play with colored lines. And filling areas.
Thank you for enlightening me.
I was relating to my experience with red / black which is only on computer screen text.
If I download a pattern with red lines, I would need to change the red to something else.