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