CREATE TABLE table_49494 ("Issued" FLOAT, "Type" TEXT, "Design" TEXT, "Serial format" TEXT, "Serials issued" TEXT)

What was the issued serial for yellow on blue design issued in 1955?
SELECT "Serials issued" FROM table_49494 WHERE "Design" = 'yellow on blue' AND "Issued" = '1955'
SELECT "Serials issued" FROM "table_49494" WHERE "Design" = 'yellow on blue' AND "Issued" = '1955'