Nonradiative dynamics of the carriers and/or excitons created by the photoexcitation in InGaN-based light emitting diodes (LEDs) with blue (460 nm, 470 nm), green (510 nm, 540 nm), and amber (600 nm) emissions were observed by using the transient grating (TG) method which is one of the third-order nonlinear spectroscopy. The dynamics of carries and/or exciton diffusion and dynamics of heat energy released by the nonradiative recombination were observed by the time profile of the TG signals in picosecond and nanosecond time region, respectively. The diffusion coefficients and the temperature change by the heat generation were detected for several LEDs and potted against the peak wavelengths of emission (In composition in active layers). Those results were compared with the results of the time-resolved photoluminescence (PL) spectroscopy. Dependence of In composition on the radiative and nonradiative recombination lifetimes, the luminescence intensities, the internal quantum efficiencies, the heat generation and conduction processes, and the diffusion coefficients of excitons and/or careers were interpreted by the model in terms of the fluctuation and phase separation of In composition.