We present the results of a Hubble Space Telescope (HST) study of dwarf galaxies in the nearby Perseus Cluster, down to MV = −12, spanning the core and outer regions of this cluster. We examine how the colour magnitude relation, structure and morphology are affected by environment for the lowest mass galaxies. On average, dwarfs in the outer regions of Perseus are more disturbed than those in the cluster core, with higher asymmetries and clumpier light distributions. We measure the (V − I)0 colours of the dEs, and find that dwarfs in the cluster core and outskirts lie on the same colour magnitude relation. We suggest that the disturbed dwarfs in the cluster outskirts are likely “transition dwarfs”, with their colours transforming before their structures. Finally, we infer from the smoothness of the cluster core population that these dwarfs must be highly dark matter dominated to prevent their disruption by the cluster potential.