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