Nursery Rhyme. Ccxvii. Riddles

[The allusion to Oliver Cromwell satisfactorily fixes the date of the riddle to belong to the seventeenth century. The answer is, a rainbow.]

Purple, yellow, red, and green,
The king cannot reach it nor the queen;
Nor can old Noll, whose power's so great:
Tell me this riddle while I count eight.