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