Vegetation fires produce biomass combustion residues, with color varying from dark black char to white mineral ash. The color-lightness of char and ash combustion residues is a qualitative parameter describing the post-fire condition of burned areas, and has been correlated with the completeness of combustion, fire intensity, and fire duration. Researchers have suggested that visual comparison of combustion residue samples with a standard grey scale would enable reliable combustion residue color-lightness estimation. This paper describes an experiment aimed at assessing if color-lightness can be estimated using a standard grey scale. Fifteen combustion residue samples with color-lightness ranging from black char to white mineral ash were collected in the Northern Territory, Australia, and visually evaluated by three individuals using a grey scale. The grey-scale scores (0-19) were compared with the mean visible (390 to 830 nm) wavelength combustion residue reflectance (0-1) measured with a portable spectroradiometer. A significant linear relationship between the grey-scale scores and the mean visible combustion residue reflectance was found (R2 = 0.816 with a linear fit, R2 = 0.936 with a logarithmic-transformed fit). This finding suggests that combustion residue color-lightness can be assessed in the field using inexpensive grey scales, and that this technique is a suitable avenue for future research on the field assessment of fire characteristics and effects.