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