This is a dust cap I made for the female XT60 connector on most of my Lipo batteries. It replaces the separate red and green silicone caps that I currently have. Based on the 20 or so XT60 connectors I had to test it on, the cap fit varied but it was never loose. 

The cap prints with a guide embossed on the top so you know where to apply color. I used red and green markers as the flag occasionally makes contact with the cap while it moves. I have not had any color come off and I have cycled the flag more than 100 consecutive times before settling on the final version. Actually, the more the flag was cycled the better it worked.

The indicator flag is 3 pieces that are one print-in-place assembly. Make sure your printer is capable of printing 0.15 mm tolerances without fusing the parts.

I also added a dust cap that does not print with the indicator guide if you don't need/want the indicator flag.

Assembly: When the print is done, free the skirt and cycle the flag a few times. After the color is dry glue the flag assembly on the cap, being careful not to get glue on the top surface of the cap or near the flag. I applied a small amount only to the outer edge of the top of the cap. 

Printing: I printed them on a Prusa i3 Mk3S in PLA at 0.2 mm layer height. Printing the cap at 0.3 mm layer height will make them fit tighter but they were a little too tight for some, not all, of my connectors. 

NOTE: Only print the indicator assembly at 0.2 mm layer height, or less,  to avoid fusing. I tested them at 0.2 mm and 0.15 mm layer heights with nearly identical results. 

I even had success printing the caps in TPU at 0.2 mm layer height. This might be the best fit as long as you are comfortable printing with flexible materials. They are very frustrating to print but once you have your print setting correct, it can be worth it. 

TPU Settings: First, I loosened the extruder idler screw as much as possible to lower the pressure in the nozzle. I also increased my z-offset by a little over 0.1 mm higher to further reduce the nozzle pressure. Lastly, I used a stock Flex profile in PrusaSlicer but reduced the bed temperature to 30 degrees. Make sure you follow any printing instructions that are recommended by the filament manufacturer.