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