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)(11,16)(12,24)(13,18)(14,19)(15,21)(17,27)(20,29)(22,33)(23,25)(26,38)(28,34)(30,35)(31,36)(32,37)(39,40) involution — undirected(1,3,6,2)(4,8,5,7)(9,11)(10,16)(12,21)(13,17)(14,30)(15,24)(18,27)(19,35)(20,25)(22,31)(23,29)(26,34)(28,38)(32,39)(33,36)(37,40)(9,12,15,16)(10,17,21,23)(11,18,24,20)(13,25,29,27)(14,26,32,33)(19,30,37,39)(22,34,38,36)(28,40,31,35)(1,4,6,5)(2,7,3,8)(9,13,15,29)(10,18,21,20)(11,17,24,23)(12,25,16,27)(14,28,32,31)(19,34,37,36)(22,30,38,39)(26,40,33,35)(1,5,6,4)(2,7,3,8)(9,14,15,32)(10,19,21,37)(11,22,24,38)(12,26,16,33)(13,28,29,31)(17,30,23,39)(18,34,20,36)(25,40,27,35)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.