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