When white light shines through a prism or through water vapor like this rainbow, the white light is broken apart into the colors of the visible light spectrum. Cones in our eyes are receivers for these tiny visible light waves. The Sun is a natural source for visible light waves and our eyes see the reflection of this sunlight off the objects around us. The color of an object that we see is the color of light reflected. All other colors are absorbed.
Light bulbs are another source of visible light waves.
This is an photograph taken from the space shuttle of Phoenix, Arizona. This is a true-color satellite image of Phoenix, Arizona. To take true-color images, like this one, the satellite that took it used sensors to record data about the red, green, and blue visible light waves that were reflecting off the earth's surface. The data were combined later on a computer. The result is similar to what our eyes see.