One vertex per element, one color per generator, with an edge from x to x·s.
(1,2)(3,7)(4,6)(5,8)(9,10)(11,21)(12,16)(13,27)(14,18)(15,20)(17,23)(19,30)(22,35)(24,37)(25,38)(26,36)(28,31)(29,34)(32,39)(33,40) involution — undirected(1,3,4,8)(2,5,6,7)(10,16,20,18)(17,32,33,31)(19,27,36,34)(21,35,38,37)(9,11,15,25)(10,17,20,33)(12,24,14,22)(13,28,29,39)(16,31,18,32)(19,35,36,37)(21,34,38,27)(23,26,40,30)(2,6)(5,7)(10,16,20,18)(13,29)(17,31,33,32)(19,34,36,27)(21,35,38,37)(23,40)(26,30)(28,39)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.