I'm pretty new to Unity but I know that the Color constructor takes 3 parameters for r(red), g(green) and b(blue). If you understand better HEX colors than rgb ones, you should use an online converter to convert a HEX color you want to a rgb color. Then you can use :
float r ; // red component
float g ; // green component
float b ; // blue component
image.color = new Color(r,g,b) ;