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