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