Quoting the manual multiskin chapter (6):
"All aircraft have individual Squadron/Staffel codes and plane ID
letters/numbers. RAF Squadron leaders carry pennants of rank."
When you install multiskin, it will write a readme for the v2.08 version
into the BoBroot, wherein you will find this text:
"In addition, individual aircraft code letters are based, as far as can
be gleaned, from historical sources. These unit-specific markings cover:
No 1, 1(C), 17, 32, 56, 85, 87, 151, 229, 238, 242, 249, 253, 257, 302,
303, 310, 601, 605, 607, 615 Squadrons.
As an example, Number 85 Squadron, led by Peter Townsend (later an
Equerry to the King, and romantically linked to Princess Margaret) was
pictured in flight with the following unit codes:
Red Section: VY-Q, VY-M, VY-U
Yellow Section: VY-O, VY-V, VY-K
Blue Section: VY-G, VY-Z, VY-J
Green Section: VY-R, VY-D, VY-E
In other words, if you find yourself in an aircraft marked 'T', then that's because it really was!"
Multiskin is controlled by the bdg.txt file. The relevant line is
MULTI_SKIN_MODE=ENABLE # valid modes: DISABLE, ENABLE, FX_FILES_ONLY, MS_FILES_ONLY. Only active when MultiSkin is installed
Setting disabled is equivalent to uninstalling but less work.