enum StateValue { Player, Wall, Box }
enum StateColor { Colors.Red, Colors.Grey, Colors.Brown }

<Button Content="Player" Background="{Binding Source=...?}" />

public Dictionary<StateValue, Color> stateValueColor =
new Dictionary<ElementState, Color>()
{
 { StateValue.Player, Colors.Red },
 { StateValue.Wall, Colors.Grey },
 { StateValue.Box, Colors.Brown }
};

[ValueConversion(typeof(StateValue), typeof(Color))]
public class StateValueColorConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        if(!(value is StateValue))
            throw new ArgumentException("value not of type StateValue");
        StateValue sv = (StateValue)value;
        //sanity checks
        switch (sv)
            {
                case StateValue.Player:
                return Colors.Red;
                //etc
            }
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
       Color c = (value as Color);
       if(c == Colors.Red)
         return StateValue.Player;
       //etc
    }
}

<Button
  Content="Player"
  Background="{Binding Source=StateValue,
    Converter={StaticResource stateValueColorConverter}}" />