Use RGBColor to specify a color from its red, green and blue components.

This gives pure red because the green and blue components are zero:

Mixing red and green gives yellow:

Color component values lie between 0 and 1.

When all of the color components are 0, you get black:

When all of the color components are 1, you get white:

Mixing different amounts of each component gives different colors:

This draws a sphere:

This colors the sphere red:

This draws a sphere at coordinate {1,1,1} with a radius of 1/2 (PlotRange specifies the extent of the drawing area; you can ignore it for now):

Change the coordinate to draw the sphere somewhere else:

Table makes arrays of things. Use Table to draw a whole array of spheres.

This makes an array of 3 numbers:

With two “indices”, you get a two-dimensional array (an array of arrays):

This uses Table to make a one-dimensional array of spheres:

Add an index to get a two-dimensional array of spheres:

Add a third index to get a three-dimensional array of spheres:

You can remove the PlotRange; without it, the drawing area is automatically made just large enough to contain the spheres:

This gives a one-dimensional array of colors that vary from almost black to red (dividing by 5 keeps the color components between 0 and 1):

This gives a two-dimensional array of colors:

Use the same strategy to color the spheres in an array:

Manipulate puts an interactive interface onto a piece of code.

This draws a sphere with radius 1/2:

Make the radius interactive by wrapping the code with Manipulate, replacing 1/2 with the variable r and specifying that r goes from 0 to 1. Drag the slider to change the radius of the sphere:

Do the same thing with the array of spheres:

Deploy the Manipulate to the Wolfram Cloud, where anyone with a browser can use it:

Click the link in the output to visit the site.

Tell the world about your creation by sharing the link via email, tweet or other message.