Planet coloring tools are used to change the color of a planet's atmosphere, ocean, or land. Once you have aquired the proper items, you can pick from these eight "flavors": blue, cyan, green, orange, pink, purple, red, or yellow. You can make any combination of colors you wish. However, one aspect of the planet can only be one color. Using more than one color on any one part of the planet will merely override the old one, as opposed to mixing them. You also can terra-color your home planet. The terrascore of the planet can influence the shade of the colour.
Although these tools are not dangerous in any way, using it on a alien planet will subtract the relationship points on the screen as if the user is deploying dangerous tools on the planet, probably due to the fact they do not want to see their planets "made ugly" by the player. Continued usage of coloring tools on planets belonging to another empire can even lead to war.
Three of them (Skies of Red, Purple Terra-Coloring, and Deep Blue Sea) will be given to you automatically if you choose the "I want to paint planets" mission from your homeworld.
The rest are found the same way as artifacts: by visiting a planet with yellow radar waves coming out of it, using the radar to locate the item, and then using your Abduction Beam to acquire it. They have the same appearance as terrasculpting tools, so you can't be sure what you will get.
It is also possible to get them by cheating. Typing "spacecreate" in the cheat box will give you all planet coloring tools along with the planet sculpting tools.