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