One vertex per element, one color per generator, with an edge from x to x·s.
(1,2)(3,6)(4,8)(5,7)(9,10)(11,20)(12,24)(13,29)(14,19)(15,21)(16,25)(17,35)(18,27)(22,31)(23,37)(26,38)(28,36)(30,34)(32,39)(33,40) involution — undirected(2,6)(3,5)(7,8)(11,21)(12,25)(13,27)(15,31)(16,24)(17,36)(18,29)(20,32)(22,39)(23,40)(26,30)(28,35)(33,34)(37,38) involution — undirected(1,2,4,8)(3,6,5,7)(9,11)(10,15)(12,26)(13,30)(14,22)(16,34)(17,37)(18,38)(19,32)(20,24)(21,25)(23,27)(28,40)(29,33)(31,36)(35,39)A Cayley diagram is a choice, not a fact about the group. Another drawing of this group — in a book, or on a different generating set — may look nothing like this one.