Lines 1 to 5 each use 3 pairs. That's pairs 1 to 15 white blue to Black slate.
Line 6 uses Y Bl for TR and YO for A lead and OY for lamp lead
Line 7 uses Y GR for TR and VB for A lead and BV for lamp lead
Line 8 uses V Or for TR and VG for A lead and GV for lamp lead
Line 9 uses VBr for TR and VS for A lead and SV for lamp lead

The VGr and VBr are spare pairs

The second strip of keys buttons 10 to 14 use 3 pairs each and Button 15 uses YBL for TR and YO for A and L
Button 16 uses YGr for TR and YBr for A and L
Button 17 uses YSl for TR and VBl for A and L
Button 18 uses VO for TR and VGr for A and L
Button 19 uses VBr for TR and VSl for A and L

There are no spares on the 2nd strip of buttons.