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