This is, believe it or not, an ice cube. But it has been colored in a special way.
Let's start with the concept of primary colors. Primary colors are those that can be mixed to create other colors. Primary colors should be chosen in a way as to maximize the other colors that can be created.
You may think of the primary colors Red, Blue and Yellow. With Blue and Yellow, for example, you can obtain Green. This is if you are working in paint or ink or colored pencil, for example. These are sometimes referred to as the "subtractive" primaries, since the artist is usually starting from a white (or off white) paper or canvas. That means that the bare paper reflects all colors of light, a situation that our eyes interpret as the color White. As you add paint (or whatever) to the canvas, it subtracts from the colors the paper reflects.
In the digital world, we have come to regard the primary colors as Red, Green and Blue. Rather than colors of paint or pigment, these are colors of light. They happen to be the colors that our eyes are most receptive to. These are "additive" primaries. The idea is that you start with a blank (White!) screen and add colors to it. If you add Red and Green you get. . .Yellow! Surprised? I certainly was. If you add a little less Green to the Red, you get orange. Remember, though, that we are adding light. Think of colored lights on a stage. If you have Red, Green and Blue lights, the set and the actors appear to be bathed in White light.
This photograph was originally or an ice cube. Ice cubes tend not to have much color, so it could just as well be considered a Black & White photo. I used a Photoshop tool called a "gradient map" to add the primary colors (RGB).