There are multiple requirements you will need to do in order to get this achievement.
In the main menu of the game you will need to select Showroom. This can be accessed in the Single Player or Multiplayer Menu and then selecting XBox Live.
You will then need to Re-Spray at least one car. To do so simply press the
button and choose a colour of your choice and then press
. You will notice here at the bottom of the screen that you can change the style of the Car as well. At this moment in time you can only have the Car Solid.
You will now need to go online and win 1 online race with the Car you wish to re-spray in a different style. Once you have won an online race, return to the showroom and then press
again to re-spray. You will now be able to access the Metallic feature. This is done by pressing
or
. Apply that feature.
Lastly you will need to play another online race and come in either 1st, 2nd or 3rd with a Car that is in a Pink Shade of colour. Light or Dark. You may be able to complete this requirement the same time as winning 1st place with the car you wish to apply a Metallic Feature on.
The achievement will unlock once you have met the last of the 3 requirements.