Please help me analyse spectrogram
The spectrograms look different because they use:


Different parameters for the FFT size and hop size (window overlap ratio).
They simply use different palettes. The spectrogram gives you an array of numbers, which are scaled and map to a color palette to produce a color image. Matlab's colormaps are listed here - by default it uses "jet" ; so the time-frequency bins of lowest energy are colored in blue, and those of highest energy are colored red.