Though not specifically stated (but implied within its parameter descriptions), collision is only for Actor type objects. The class given can be used to specify a particular type of actor (or 'null' can be given to indicate any or all Actor types). You will need to get the background image of the world (presuming that is where the Color object you are checking is at), get the Color from it and compare that color to what colors are of interest.

The above is an example. 'actor' should be replaced with the name of the referenced intersecting actor and 'm' and 'n' should be replaced with either some constants or with variable names that represent some computed values.

So , the actor should be my car and n, m coordinates where i found the specific color . But how can i put a personalized color instead of "Color.BLACK." ? it is a method which helps me to declare a found color , like asign it to a variable for example "color 1" and after simply put "Color.color1" there ?

The actor would be that which the car collides with (code in the Car class). The 'm' and 'n' are the horizontal and vertical offsets from the top-left corner of the image at which you wish to grab the color from. You can simply replace 'Color.BLACK' with 'color1', provided it is assigned the color you wish to check for.

Please show what code you are attempting (minimum -- the method the code is in).

this is the car code import greenfoot.*; import java.lang.String; public void act() { if ( Greenfoot.isKeyDown("up") ) { move(3); } if ( Greenfoot.isKeyDown("down") ) { move(-3); } if ( Greenfoot.isKeyDown("right") ) { turn(3); } if ( Greenfoot.isKeyDown("left") ) { turn(-3); } Color color1 = new Color(34,177,76); if (color1.equals(masinutza.getImage().getColorAt(460,385))) { setLocation(106 , 448);}} }