Temperature-time histories of burning single coal particles can be obtained with multi-color (multi-wavelength) optical pyrometry. With this method, a number of different temperatures can be deduced from the resulting number of two-color ratios. However, these two-color temperatures do not always agree, causing considerable uncertainty in the temperature measurement. This work used a three-color pyrometer and focused on identifying and minimizing the causes of disparity among the three deduced temperatures. Components of the pyrometer (such as dichroic filters, interference filters and photo-detectors) were modeled mathematically, taking into account their wavelength-dependent properties. The pyrometer was calibrated with both a high-temperature pre-calibrated tungsten lamp, and a moderately-high temperature blackbody cavity, to span the temperature range of interest in pulverized coal combustion. Temperatures were deduced based not only on a suitably-modified pyrometric signal ratio method but also, on a similarly modified pyrometric signal non-linear least-square method, to provide comparison. Results are exemplified by presenting radiation-signal-time and temperature-time profiles of single particles burning in air. The variation of the projected luminous area of burning particles was also computed using both methods, and area-time profiles are presented herein. The char particle emissivity was either treated as a quantity independent of the wavelength (i.e., assuming gray-body behavior), or as a quantity assumed to depend linearly on the wavelength and using pertinent published emissivity data. Finally, a sensitivity analysis was performed to investigate individual effects of parameters, such as the calibration method, the wavelength dependencies of filter transmissivities, and the photo-detector responsivities on the pyrometric signal ratio method temperature consistency. (C) 2011 The Combustion Institute. Published by Elsevier Inc. All rights reserved.