import - Haskell deriving additional instances for imported datatypes -

i'm relatively new haskell. write clone of card game uno , want pretty coloured output of card. do

import system.console.ansi 

which provides

data color = black            | red            | green            | yellow            | blue            | magenta            | cyan            | white            deriving (bounded, enum, show) 

now want add deriving (ord, eq) well, write in source file of imported package, there should easier way this. don't have clue keywords google or in book.

no need edit library. in source file, state:

instance eq color   x == y  =  fromenum x == fromenum y  instance ord color   compare x y  =  compare (fromenum x) (fromenum y) 

explanation: fromenum function on enum returns int (black -> 0, red -> 1, etc.). integers equality-comparable , ordered.

edit: @rampion's version, in comments, prettier:

instance eq color   (==)  =  (==) `on` fromenum  instance ord color   compare  =  compare `on` fromenum