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