Taking advantages of high speed RGB video cameras, the two-color method can be implemented with a relatively simple setup to obtain the temporal development of the two dimensional temperature and soot (KL) distributions in a reacting diesel jet. However, several issues such as the selection of the two wavelengths, the role of bandpass filters, and the proper optical settings, etc. should be known to obtain a reliable measurement. This paper, at first, discusses about the uncertainties in the measurement of temperature and KL distributions in the diesel flame by the two-color method using the high speed RGB video camera. Since n-butanol, as an alternative renewable fuel, has the potential application in diesel engines, the characteristic of spray combustion of diesel-butanol blends under the diesel-like ambient conditions in a pre-burning constant-volume combustion chamber is studied. The Red and Blue channels of the high speed video camera are chosen for the two-color imaging because their response curve has a much smaller overlap. When adding the n-butanol into the neat diesel, the experimental result shows that the flame has a lower integral level for both flame temperature and soot density than neat diesel flame, owing to both increases in the fuel-borne oxygen and elongated ignition delays. In order to study the effect of LTC (Low Temperature Combustion), the ambient O2 concentration is set at four levels: 21%, 18%, 15% and 12%. The results show that with the decrease of O2 concentration, the flame temperature has a dropping tendency, while the KL (soot density) factor has a complicated behavior as a result of soot oxidation rate variation.