Can someone offer some kind of historical commentary on this broadside. My guess is the whigs are the american rebels? Who are the blues? Holyroyd? (That was the spelling, with the 'y')

(1780, Parliamentary elections at Coventry; AIR -- Rule Britannia)

Now loyal Britons lend your Aid
Nor let the dastard Whigs e'er boast
Their's is the Charter, it always shall be said
That loyal Britons rule the roast

Rule ye Blues, stand firm to George our King
In ceaseless numbers ever sing

True Britons nere can conquer'd be
They'll make all Foe before them fly
And well known Traitors to their Confusion see,
That sooner than we'll turn, we'll die

Our streaming flag shall make them pale
And terror seize the rebel throng
To see the Standard of the Blue prevail
And norne in awful Pomp along

Up-rais'd shall virtuous Holroyd pass
And thronging Myriads bless his Name
Whilst each rebellious Knave and Whigish Ass
Shall hide his recreant Head for Shame

from
http://bodley24.bodley.ox.ac.uk/cgi-bin/acwwweng/ballads/image.pl?ref=G.A.+Warw.+b.1(506)&id=24775a.gif:24775b.gif&seq=1&size=1