Minnie and Tootsie wear there buddy belts all the time and I've never used a liner. so, i'd recommend to try it without the liner first.
the color you see in the pic is probably an older color that isn't available anymore.
I recommend an online boutique called wetnoseboutique to buy your first buddy belt. you can call her up on the phone to order and she is very nice. ( forgot her name, but theres only one lady that runs it ). and , if the fit isn't good , and you just try it on your dog for fit... she will let you exchange it without any problem. you can ask her about color choices too . and she'll help you figure out fit. just a suggestion because some places may not be good at exchanges like her ... seeing its your first time ordering one. the size chart can be alittle off sometimes.