Losing color in a planted tank? That doesn't really make much sense, but who knows.
From the Glofish website.
GloFish® fluorescent fish absorb light and then re-emit it. For best results when displaying these extraordinary fish, we suggest the following:
Daytime Viewing – A traditional white aquarium light (such as a fluorescent or halogen light) is ideal for daytime use, although an actinic (blue wavelength) light works great too! Because GloFish® fluorescent fish absorb light and re-emit it, the fish's color will appear brighter and more vibrant as the amount of light used is increased.
Nighttime Viewing – In cases where the room is completely dark, a black light will create the appearance that the fish are glowing in the dark. This is a truly stunning and beautiful way to display your ornamental fish at night! But please remember that the black light will only be helpful in a completely dark room. Using a black light during the daytime will not result in the fish demonstrating its true beauty.
Please note: Aquarium lighting should not be left on continuously, as fish benefit from alternating periods of light and darkness, just like people.
Also from the website one reason I will
NEVER buy these fish.
GLOFISH® FLUORESCENT FISH LICENSE NOTICE
The GloFish® fluorescent ornamental fish are intended solely for visual enjoyment as aquarium fish by end users who have purchased these fish from authorized resellers, and not for commercial reproduction. These fish are the subject of various intellectual property rights owned or controlled by Yorktown Technologies, Inc. (“Yorktown”

, both in the U.S. and internationally. These rights include (1) patent rights, including published patent applications (2) copyrights; and (3) trademark rights, including slogans and service marks.
By accepting these fish, and as part of the consideration therefor, the recipient agrees: (1) not to, breed or propagate these fish, permit or encourage others to breed or propagate these fish, or otherwise intentionally engage in any activity that may result in or lead to the breeding or propagation of these fish by anyone without the express written consent of Yorktown; (2) not to sell or transfer these fish to anyone in the State of California, or to possess or otherwise engage in any activity that results in the possession of these fish in the State of California.