Is colour polymorphism advantageous to populations and species?

I am writing in response to an article by Bolton, Rollins and Griffith (2015) entitled ‘The danger within: the role of genetic, behavioural and ecological factors in population persistence of colour polymorphic species’ that was recently published as an Opinion under the NEWS AND VIEWS section in Molecular Ecology. Bolton et al. (2015) argue that colour polymorphism may reduce population fitness and increase extinction risk, and emphasize that this is contrary to predictions put forward by Forsman et al. (2008) and Wennersten and Forsman (2012) that the existence of multiple colour morphs with co-adapted gene complexes and associated trait values may increase the ecological and evolutionary success of polymorphic populations and species. Bolton et al. (2015) further state that there is no clear evidence from studies of ‘true polymorphic species’ that polymorphism promotes population persistence. In response, I (i) challenge their classifications of polymorphisms and revisit the traditional definitions recognizing the dynamic nature of polymorphisms, (ii) review empirical studies that have examined whether and how polymorphism is associated with extinction risk, (iii) discuss the roles of trait correlations between colour pattern and other phenotypic dimensions for population fitness, and (iv) highlight that the causes and mechanisms that influence the composition and maintenance of polymorphisms are different from the consequences of the polymorphic condition and how it may impact on aspects of ecological success and long-term persistence of populations and species.