Abstract: The present invention concerns the detection of resistance in a living organism, e.g., herbicide resistance in weed crops. Based on non-separated compounds obtained from an organism, e.g., an extract from a plant, a color development is generated. The color or shade developed is dependent on the compounds of the organism. By comparing the color or shade of the extract obtained from an organism with a standard color scale developed with respect to the same organism, it is possible to determine if the organism is resistant to a pesticide, e.g., a herbicide. The invention also concerns a method of providing a standard color scale for material from a living organism that has been exposed to stress, e.g., a pesticide. As assay kit for the determination of whether material from a living organism is resistant to a pesticide is also described. The present invention may be used by farmers or advisors to test if the plants have developed resistance to a herbicide.