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