Studies were performed to evaluate the suitability of a commercial gouache as an external marker for termite workers in lab assays. Dyed and non-dyed termites presented similar survival for the first 300 minutes since the experiment has began, and differed after this time. Mortality did not differ for termites dyed in two different colours from the same brand of gouache. It was concluded that commercial gouache could be a suitable marker for Cornitermes cumulans (Isoptera: Termitidae) termites, provided following restrictions were applied (i) tested hypotheses did not rely on times to death greater than 300 min., or (ii) experiments included "sham-dyed" termites (i. e., a "control" group with "dyed" individuals, rather than the tradicional control group composed by non-dyed individuals).