The paper examines how emotional reactions (spiritual sense) to colour within religious architectural like mosque can be empirically measured and the best colour palette for mosques proposed. First, the concept of colour and its status in the Nasir Al-Molk mosque is defined based on a descriptive-analytical approach. Then, an experiment has been performed using quantitative electroencephalography waves (brain map), between the statistical population with 18 people sample size. The analysis of the data extracted showed a significant difference between the two conditions (Normal) and (Test) in the frequency of beta, theta and alpha. 'The highest increase in alpha' and 'the highest decrease in the theta/beta parameter' (Two criteria for promoting spirituality) belong to the 'North Porch' image. Other priorities, respectively, are South Porch, Eastern Corridor, Eastern Shabestan and Western Shabestan. So 'turquoise', 'green' and 'blue' colours (colour spectra of image 'North Porch') increase the spiritual sense.