Since this is a
DVC forum, I presume you are staying at a DVC resort. Almost all the DVC resorts have COLORED replacement Magic Bands available at the front desk. Just go ask for some. At other hotels they usually only have grey.
You can also buy a colored one for about $15 at any ticket window at the park entrances and at the Transportation Center.
You can also go into the gift shops at ALL the hotels and resorts, and some gift shops in the parks, and buy 'special collectors' Magic Bands. These usually cost about $25 each.
If you go to the Front Desk they will connect the Magic Band with your account. If you buy one, just go to your My Disney Experience App on your phone or computer, disneyworld.disney.go.com, and go to your account and read the numbers on the back of the magic band and connect them to your account to activate them.