Mine's the Green One, Yours is the Blue

I recently found out something about my marriage that I wasn't previously aware of. It's colour coded. I had made lunch one morning and packed them into sandwich boxes, when I picked up the remaining box at lunch time it wasn't my sandwich. I asked my wife why she had eaten my sandwich and she said "it was in my sandwich box". "Mine's the green yours is the blue".
Well! I hadn't realised, my wife has colour coded everything and I didn't even know. I knew my toothbrush was the blue one, hers the green. When you live with someone you have to know which toothbrush is yours that's standard. I hadn't realised this whole colour coding extended throughout our lives. How have I managed to not notice this? There are sandwich boxes, toothbrushes, thermos cups, how have I not noticed? I think I've got it sorted now though eh?