What you are asking about is INCREDIBLY DIFFICULT. Because these two items already have color, and are likely different fiber content, the chances of success for a very experienced dyer are slim and none. And that isn't taking into consideration what they actually are, this answer applies to two tee shirts with color trying to be dyed the same color...
You might try watering down acrylic paint, to get them closer to the same color, but paint isn't reversible and on that texture it will be difficult at best.
my advice is keep shopping until you find pieces that match or live with these being slightly different.