With my vision issues I often have issues with the rulers anyway. Dealing with "Olfa green" is actually pretty easy. I use a piece of paper or an envelope on one/the cut side of the fabric. Not shown in this picture but sometimes overlapping that top edge help too if your cut is wide enough.
I'll also mark/reinforce my cutting thickness with a piece of tape on my ruler, helps me be consistent and lets me see/count the grid where I can.