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