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