This is factually wrong. Big Jim has said about Hyper Sonic “That is a colt.” in a tweet. But he is misinformed about this.
At the end of 2019, all episode scripts of My Little Pony: Friendship is Magic got leaked. In the script of “The Ending of the End - Part 2”, Hyper Sonic is mentioned to be female:

“Hyper Sonic and the pegasi she rescued face Feather Flatterfly and the other adult pegasi.”

Hyper Sonic also appears as a filly in the finished episode (eyelashes). Big Jim, when questioned for his tweet, has claimed that colts can have eyelashes, too, and that DHX has never seen eyelashes as a feature that’s exclusive to fillies. This would make Hyper Sonic the first colt with eyelashes in the show, however, the episode script confirms that she was always intended to be a filly.
Big Jim always strongly insisted that Hyper Sonic is a colt and just repeated the same thing every time he was asked. But the episode’s writer, the storyboarders and the animators have all decided that Hyper Sonic is a filly and Big Jim does not have the authority to overrule these decisions.
I don’t understand how Big Jim can be so badly misinformed about the show he directed for so many years. Some speculate that he was merely trolling the fandom when he said that about Hyper Sonic, others say that he tried to save face after an animation error involving another foal happened in the last episode (Lil’ Cheese, mentioned as colt in the script of “The Last Problem”, but was accidentally animated as a filly) by citing eyelashes as a possible colt feature.
It’s impossible to tell whether Big Jim is misinformed, was trolling, tried to save face or felt the need to suddenly enact a misguided authority as director of the show. But the information in the script makes this a clear case. Hyper Sonic is a filly.

@007Ben
i am pretty damn late to this but actually! he’s a colt. jim miller has said so himself

This image is tagged for both colt and filly. Should just be filly.
 
https://derpibooru.org/1893663?q=lemon+crumble%2C+gameloft&sd=desc&sf

Taylor Diane Robinson

Lemon crumble

@Background Pony #81FE  
A little typical, but I like it.
 
Also, totally headcanoning that she and the unicorn colt we saw in the same episode are siblings.

Name suggestion- Goldenwind