Time-frequency representation of sound signal using Matlab
I believe that this "color graph" you are looking for is a spectrogram (although it looks to me more like a scalogram, but you did not mentioned wavelets). Let me give you an example in MATLAB of obtaining such plot:

load handel
nfft = 512;  
noverlap = 128;
win = hamming(nfft);
spectrogram(y, win, noverlap, nfft, Fs, 'yaxis')
colormap('jet')


So first line is loading of some standard test recording, it gives you two variables: Fs (sampling frequency) and y (your signal). Next you define length of your analysis: nfft in your Short Time Fourier Transform and by how many samples you want to shift your analysis window. When defining window you can use variety of them (simply check in MATLAB help), I've used most common one: Hamming window. Last line is for setting colour representation.

Computation of spectrogram is very straightforward, please refer to help for more details: click. The last argument 'yaxis' tells MATLAB to use horizontal time axis and vertical for frequency.

Having that you can play with length of your analysis window and the overlap. You must though understand one, most important thing: better resolution in time (short window) yields poorer resolution in frequency domain and vice versa - that's a trade-off.

In the end you should get something like:



EDIT:

Because you would like to obtain the scalogram, here's how to do it in MATLAB. Most important thing - you must have Wavelet Toolbox installed!

% Definition of signal consisting of two sinusoids
f1 = 10;
f2 = 40;
Fs = 1000;
t  = 0:1/Fs:1;
y =  sin(2*pi*t*f1) + sin(2*pi*t*f2);

wname = 'morl'; % Choosing the wavelet
scales = 1:1:128; % Defining scales
coefs = cwt(y, scales, wname); % Get wavelet coefficients

wscalogram('image', coefs, 'scales', scales, 'ydata', y); % Get the scalogram, together with time domain signal overlayed
colormap(jet) % Set the colormap


As a result you will get something like: