I was a bit unhappy with the existing extruder indicator of my A1 and created this set of three extruder indicators as a replacement. Each one shows extruder activities very clearly. I suggest to print them in a combination of black / yellow or any other high contrast colors.

Please remove the support structure carefully from the back side before applying them to your A1 as the structure is quite small.  I used the small blade of a swiss-army knife, but other tools may work well too.