As a GM I enjoy seeing players take this disadvantage. There are a couple types of players that take this disadvantage. The first one is the player that wants to round out the concept of their character. They look for chances in the game to play Colorblindness. The other type of player is the one that thinks they are getting (-10 points) for a disadvantage that requires no role playing. If you have read any of my previous posts you know that role playing within the game is very important. As a GM I see this as an opportunity to show that Colorblindness can be role played.
Colorblindness in GURPS is a disadvantage worth (-10 points) to the character. The character is unable to see any colors. This is considered to be total colorblindness. The character is also at a -1 on most situations, using the Artist, Chemistry, Driving, Merchant, Piloting and Tracking rolls. The question then becomes, what does the GM do to give the player an opportunity to role play Colorblindness?
In the past I have placed color obstacles in front of the player. Most of the time the obstacles are choices that have to be made, like drinking a red potion or cutting that blue wire. Even if there are others present in the party to help the character determine the color, the player still has the opportunity to role play. Just the simple act of asking for help in identification of the color is role playing. Sometimes the help that is given may not always be correct and then more role playing follows between the players. So regardless of the type of player this somewhat innocuous disadvantage can contribute to some great adventures.