This article aims to quantify the colour discrimination ability by using Total error scores (TES) to categorisecolour discrimination level into superior, average or inferior levels under three different types of light sources, with different spectral power distribution. Colour discrimination was investigated using Farnsworth-Munsell 100 hues and compared upon three light sources: compact fluorescent light (CFL), fluorescent light (FL) and light emitting diode (LED). Total error score calculated and pattern of colour caps misplacement plotted used the web-based scoring method (http://www.torok.info/colorvision/fm100.htm). Total error score (TES) for three types of light sources (TES for LED 58.00 ± 18.67, FL 80.00 ± 19.27 and CFL 127.25 ± 28.02) were significantly different [One-way ANOVA (F=9.98, P<0.05)]. Tukey post hoc analysis showed that there was significant difference between compact fluorescent light & fluorescent light, and between compact fluorescent light & light emitting diodes. Variation of the mid-point cap was smaller for both types of fluorescent lights but higher under light emitting diodes. Fluorescent light and light emitting diode with 4000K correlated colour temperature showed average colour discrimination with mean total error score range between 20 to 100, while compact fluorescent light showed inferior colour discrimination with mean total error score of more than 100. Different light sources with different spectral power distributions affected the colour discrimination differently. This cross-over study design using the same subjects, the same testing tool and the same examiner suggested that subject responded differently towards fluorescent light and light emitting diode light source in the total error score of the Farnsworth-Munsell 100 hues.