why do they care what color it is?
Skating aside, my MIL never liked seeing a little kid wearing any kind of black-colored clothing. She came to accept it for skating because it was practical and well-accepted. Still, she never bought a Christmas dress in black for any of my DDs and made a point of telling me that. I've relaxed that rule when it comes to ordinary clothing but I think about it whenever I see a pretty dress.
For Moves or Dance tests, I like skaters to wear a plain black dress, but for freestyle the color should reflect the program/music, imo. While black is practical, it also has connotations of mourning, seduction and evil. Skating to "Walking on Sunshine" while wearing a black dress doesn't quite reflect the spirit of the program.
For her dance tests, one of my DDs wore a hand-me-down dress that Sk8Dreams gave us a few years ago. The plain, red-plaid pattern was a HIT because it was unusual - no sparkles or glitter and it fit beautifully with a slightly-longer skirt than most. One of the judges actually remarked on it to me later because it was different and she skated beautifully.
You might me able to find spandex with glittery diamonds already printed on the fabric, which would make the whole dress less over the top and save you time and money. Just an idea. You could make the diamond pattern bigger so you have fewer sparkly lines and flowers. Craft stores sell the flower-shaped plastic stones in various sizes.
I think it depends with knockoffs - Posters have remarked about how the Chinese eBay sellers are ripping off others' designs. You seem very capable of coming up with your own designs and ideas. There's no harm in studying others to get new ideas, especially when you're just getting started.