Chroomonas coerulea is a species of cryptophyte alga in the family Chroomonadaceae, distinguished by its blue or blue-green coloration, as referenced by the specific epithet coerulea, meaning sky-blue or cerulean. The blue-green to blue color of this species results from the predominance of phycocyanin or phycoerythrin 569 phycobiliprotein — pigments derived from its secondary red algal endosymbiont — combined with the other accessory pigments typical of cryptophytes. Many Chroomonas species appear in shades of olive to brown, making the distinctly blue-tinted coerulea somewhat unusual within the genus and useful for field identification by experienced microscopists. Chroomonas coerulea inhabits freshwater and possibly brackish environments in Europe, contributing to the micro-phytoplankton and picoplankton communities of its habitat. Cryptophyte algae are nutritionally valuable components of aquatic food webs and are frequently used as high-quality food sources in aquaculture and zooplankton culture due to their polyunsaturated fatty acid content. The species has not been assessed by the IUCN, consistent with the treatment of microalgal species.