How to place id's to multiple same-coloured markers

edit

We are doing a study end project, we're not used in programming so we're kinda stuck. Our project is based on real time markers detection which reflects light (image tresholding). After three markers are detected using picamera, centroids of contours should be connected and after that, angle between such made lines should be measured. Here comes the question- is there any solution to attribute id's to markers given as contours so they won't be mistaken after changing mutual position (now found contours are always numbered from left to right?? Please help