I love my Martelli mat - yellow with navy lines on one side, lavender with white lines on the other. I mostly use the yellow side. It's held up well over the years. Like you I use the lines for lining up rather than measuring, and I find them very easy to see.

I just realized, I also have a gray mat with white lines. I actually like that one a lot.

The mat I am using right now is light blue on one side and pink on the other. I also have an olive green on one side with yellow on the other side. This one has black lines that are easy to follow. I have not been able to distinguish much difference between most of the cutting mats that I have had. As long as the lines are clear.