in hilchois bosor vecholov their is a simon given for milchigs and the to put scratches onto the handles and since your not aloud to change the simonim if you find a utensil with scratches you knoe its milchig the siman is “ch”aritzim “ch”alavi
now a days the universal siman is as ma brought red for meaty and blue for dairy having it different is a problem lehalocho