(* Assumption->None, Method->"Spa****"; *)
Style[#, RandomColor[]] & /@ Characters["Mathematica"] // Row
or credit to Mark
StringForm[
"`1``2``3``4``5``6``7``8``9``10``11`"
, Sequence @@
(Style[#, RandomColor[], 56, Italic, FontFamily -> "Times New Roman"] &
/@ Characters["Mathematica"]
)
]