The present study was carried out to determine the effect of synthetic red food color on chromosomal behaviour on root tips of Allium cepa L. The common synthetic red food colour at different concentrations, 500, 1000, 2000 and 3000ppm was prepared and used to study various behavioral changes of chromosomes. Initially the mitotic cell division was much affected and mitodepressive effect was found to be increased in all the studied concentration and simultaneously the frequency of abnormality was found to be higher when the compared with control. It is also observed many important abnormal stages like DNA vacuolation, Elongated nucleus, Clumping, Diagonal Metaphase, Disorientation, Laggards, Chromosomal bridges, Diagonal Anaphase, Binucleated condition in different stages of mitotic stages. Most predominantly the DNA vacuolation (22.97%) and elongated nucleus (12.97%) were found in the study and synthetic food colour considered to be highly toxic to chromosomes and cell division.