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