An 18th Century Allusion to Lighting Farts

[Thomas Bridges,] A Burlesque Translation of Homer, 3rd ed., vol. 1 (London: S. Hooper, 1770), p. 111:

I'th' int'rim, fond of mischief telling,
The rainbow-goddess flies to Helen:
Most modern farts I ever knew,
When set on fire burn only blue,
Or simple red, but when behind
This nimble goddess lets out wind,
You see not only reds and blues,
But all the colours painters use.