Hi, ash is a dull colour. If your hair has red pigment in it, a regular brown will probably bring out brassy or red tones. Ash colour having green in it will tone these red tones. The best way to figure out the difference between brown and ashbrown is to compare the 2 dye boxes with the colour swatch on it and you'll see that ash is a rather dull brown colour, in comparrison to reg brown. Good luck