FindSlot only returns one slot, so it looks like it finds the Left Side "Sleeve" Slot first, and returns that, and doesn't continue looking for more than one slot with that name.
ExposedList<SlotData> slots = teamCrowdNoneColor.skeleton.slots;
for (int i = 0, n = slots.Count; i < n; i++) {
SlotData slot = slots.Items[i];
if (slot.name == slotName) slot.SetColor(Color.green);
}
Alternatively (if you need to change colour a lot), search once, save those slots away first.