How to make random colors?

How to make a set of 4 random RGB colours? In freeglut or glut. Or opengl.

Generate 4 random float values in [0, 1] and pass them to glColor4f().

well it is not so straight forward.
I have 6 colors.
blue, green, yellow, light blue, white and red.
I want to create a set of 4 colors from them.

colours array[6] = {sblue, sgreen, slblue, syellow, sred, swhite}

;

I got this. All the members are the objects of my structure colours whose members are R, G, B.
How can I do it?

struct colours
{                        
       int red;
       int green;
       int blue;
           
}sblue, sgreen, slblue, syellow, sred, swhite;
//--------------------------------------------------------------------------------------------------------------------
int createrandomcolors()
{
    sblue.red = 0; sblue.green = 0; sblue.blue = 255;
    sgreen.red = 0; sgreen.green = 100; sgreen.blue = 0;
    slblue.red= 0; slblue.green = 255; slblue.blue =255;
    syellow.red =265; syellow.green = 140; syellow.blue = 0;
    sred.red =1; sred.green = 0; sred.blue = 0;
    swhite.red=1; swhite.green = 1; swhite.blue =1;
    colours array[6] = {sblue, sgreen, slblue, syellow, sred, swhite};   
}

So what you want to do is to pick 4 out of those colours at random? That was completely impossible to guess from your original post.

Just generate 4 random integers, to use as indices for an array of colours?

Sorry about that. I suck at making posts.
could you please tell me in detail how to do that?

Ref: http://www.cplusplus.com/reference/clibrary/cstdlib/rand/

Or you can use the built-in noise function in the shader language.