With dressage, you can have any color you want...as long as it's black. Definitely not a dressage bridle! It is cool looking though.
There is no such rule that dressage tack has to be black!
2. For Training, First and Second Level tests and FEI Pony tests, a plain snaffle bridle is required with a regular cavesson, a dropped noseband, a flash noseband (a combination of a cavesson noseband and a dropped noseband attachment) or a crossed noseband. Except for the FEI Pony
tests, a crescent noseband is also permitted at these levels. Except for the crescent noseband, buckles and a small disk of sheepskin, which may be used in the intersection of the two leather straps of a crossed noseband, the headstall and cavesson/noseband of the bridle must be made entirely of leather or leather-like material. A padded cavesson/noseband and crownpiece are allowed.
A browband is required, and except for the parts that attach to the crownpiece or headstall, is not required to be made of leather or leather-like material.
So technically there is no reason why you shouldn't be able to use the mint trimmed bridle - it's very pretty and for me the 'old fashioned' person to like it is quite remarkable. Not sure if I would use it in a test, however with the amount of bling found on dressage horses these days it's actually quite discreet.
Oooh! I've just noticed it comes in brown leather as well with the mint lining. hmmmmmmmmmmmmm! I feel a credit card transaction coming on.