Here is the first airmail label from Bolivia. Interesting that this labels is same design and size like Colombian label just in blue color. And Colombian labels are in green.
Year: 1930, Gummed. Günter Mair's catalogue no: - BLV-A-1, perforated H 12 ¾ , V 11 ¼ , sheets of
25(5x5), grey-blue/white, 4****