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