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