Niger FDC Envelopes

Item

Title
Niger FDC Envelopes
Description
1972 On November 23, 1972, the Republic of Niger issued a set of air mail stamps in honor of Jean de la Fontaine, including the three specimens pictured below, each on a first day cover and each in a numbered series of 2000. $30 from Alexandre Przopiorski, August, '99.

The stamps in each case seem to include three colors, one of which is black and one brown. A strong brown foreground stands against a sketchier blue or green background. Are there more in the series?
Source
$30 from Alexandre Przopiorski, August, '99.
Date
1972