root tip was fixed in fixative for 3 hour at 4-6 degree Celsius then hydrolysed with 1N HCl for 15 min and finally stain with acetocarmine for 2 to 5 min and also try for 24 hr.
Your fixative determines whether your colouration works or not. Recommended is Carnoy's fixative or no fixation at all. Staining up to 2-7 days is possible for whole roots.