Ubiquitous systems can be characterized as providing transparency, while being context-sensitive and dynamically interactive. Evaluating ubiquitous environments involves challenges ranging from multidisciplinary areas to environmental simulations. However, few studies have been carried out on the user's feelings and moods in these environments, i.e. within mental contexts. This paper undertakes an observational case study which involves evaluating emotional responses in ubiquitous environments. A number of volunteers were exposed to stimuli with the aim of changing their mood through colors and images, in accordance with their initial emotional state. Emotional responses were evaluated by means of a hybrid approach that entailed employing different evaluation instruments at different periods of the interaction and which took account of different stakeholders. The results suggest that the approach is appropriate, although some adjustments are required for the evaluation instruments, as well for the interaction time with the environment so that it is possible to collect further data about the user's experience.