> The theorem is **NOT** about "patterns". The theorem does **NOT** say > that there is an algorithm for producing a coloring, as you seem to > think. The theorem says that **GIVEN** a map, a coloring exists *for > that map*.
May I ask if there is a practical algorithm? Clearly there is an algorithm: colour the given (finite) map in all possible ways with four or fewer colours, examine each colouring in turn until an admissible one is found. The theorem ensures that one will be found. But that would be quite impractical.
-- Madam Life's a piece in bloom, Death goes dogging everywhere: She's the tenant of the room, He's the ruffian on the stair.