The complete map coloring program follows. You can also view it online in the file YourSolverHome/examples/src/color.cpp.

#include <ilsolver/ilosolverint.h>
ILOSTLBEGIN
 
const char* Names[] = {"blue", "white", "yellow", "green"}; 
 
int main(){
  IloEnv env;
  try {
    IloModel model(env);
    IloIntVar Belgium(env, 0, 3), Denmark(env, 0, 3), 
      France(env, 0, 3), Germany(env, 0, 3), 
      Luxembourg(env, 0, 3), Netherlands(env, 0, 3);
    model.add(Belgium != France); 
    model.add(Belgium != Germany); 
    model.add(Belgium != Netherlands);
    model.add(Belgium != Luxembourg);
    model.add(Denmark != Germany ); 
    model.add(France != Germany); 
    model.add(France != Luxembourg); 
    model.add(Germany != Luxembourg);
    model.add(Germany != Netherlands); 
    IloSolver solver(model);
    if (solver.solve()) 
      {    
      solver.out() << solver.getStatus() << " Solution" << endl;
      solver.out() << "Belgium:     " 
                   << Names[(IloInt)solver.getValue(Belgium)]     << endl;
      solver.out() << "Denmark:     " 
                   << Names[(IloInt)solver.getValue(Denmark)]     << endl;
      solver.out() << "France:      " 
                   << Names[(IloInt)solver.getValue(France)]      << endl;
      solver.out() << "Germany:     " 
                   << Names[(IloInt)solver.getValue(Germany)]     << endl;
      solver.out() << "Luxembourg:  " 
                   << Names[(IloInt)solver.getValue(Luxembourg)]  << endl;
      solver.out() << "Netherlands: " 
                   << Names[(IloInt)solver.getValue(Netherlands)] << endl;
    }
  }
  catch (IloException& ex) {
    cout << "Error: " << ex << endl;
  }
  env.end();
  return 0;
}
 

Results

FEASIBLE Solution
Belgium:     blue
Denmark:     blue
France:      white
Germany:     yellow
Luxembourg:  green
Netherlands: white