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