Before

public class Triangle {
    Point p1, p2, p3;

    Triangle(Point p1, Point p2, Point p3) {
	this.p1 = p1;
	this.p2 = p2;
	this.p3 = p3;
    }

    void someMethod() {
	// do something with the Points p1,p2,p3
    }
}

After (Version 1)

public class Triangle {
    Point p1, p2, p3;
    String colorName = "";    // default is empty colorName

    Triangle(Point p1, Point p2, Point p3) {  // unchanged
	this.p1 = p1;
	this.p2 = p2;
	this.p3 = p3;
	// colorName stays empty (declaration)
    }

    Triangle(Point p1, Point p2, Point p3, String colorName) {
	this.p1 = p1;
	this.p2 = p2;
	this.p3 = p3;
	this.colorName = colorName;
    }

    void someMethod() {
	if (colorName.equals("")) {
            // do something with the Points p1,p2,p3
	} else {
	    // do something with the Points and colorName
	}	
    }
}

After (Version 2, My Preference)

public class Triangle {
    Point p1, p2, p3;
    String colorName;		// no default here

    Triangle(Point p1, Point p2, Point p3) {
	this(p1, p2, p3, "");  // default is empty colorName 
    }

    Triangle(Point p1, Point p2, Point p3, String colorName) {
	this.p1 = p1;         // same as After (version 1)
	this.p2 = p2;
	this.p3 = p3;
	this.colorName = colorName;
    }

    void someMethod() {  	// same as After (version 1)
	if (colorName.equals("")) {
            // do something with the Points p1,p2,p3
	} else {
	    // do something with the Points and colorName
	}	
    }
}