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