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