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