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