Conclusions: This study revealed a significant correlation between red-green-blue (RGB) values of tympanic membrane (TM) images and the presence of effusion in the middle ear. These results confirm that endoscopic RGB evaluation is a rapid and non-invasive procedure yielding objective results. Objective: To investigate, in cases of otitis media with effusion (OME), the correlation of the TM color changes with the presence and viscosity of the effusion in the middle ear. Methods: Endoscopic images of the TMs of 52 patients (group 1) and 52 healthy controls (group 2) were taken during their otologic examinations. RGB values of particular points were measured on the TM images of both groups. Additionally, in group 1 the viscosity of each effusion taken by paracentesis during surgery was also measured intraoperatively with a viscometer. Patients with viscosity values lower and higher than 450 cP (centipoise) were subdivided into groups 1a and 1b, respectively. Results: Study and control groups were comparable regarding the number of patients and their mean ages (p > 0.05). Statistically significant differences were found in RGB values of the TM between groups 1 and 2, but not between groups 1a and 1b.