In A New Hope, the X-Wing squadron attacking the Death Star is called "Red Squadron". Do TIE Fighters have squadron names too? If so, what are they named after (color, alphabet, number)?
Answers from the non-canon Expanded Universe are acceptable.
There are several naming conventions...
X-Wing Rogue Squadron EU works had numeric designations for them (basically, similar to USAF). Example: 233rd , 128th TIE Interceptor Squadron. And we can't forget Baron Fel's Squints, aka 181st Imperial Fighter Wing
Essential Guide series supported this convention, as did Star Wars Insider posts.
TIE Fighter flight simulator game from LucasArts had Greek lettered squadrons:
Just like Rebels having special squardons (Rogue), some Imperial squadrons had their own special designation. Such as:
And, just like Rebels, there were color themed squadrons. Some RPGs used numbers, but some used colors, e.g. Yellow squadron
EU/Legends canon calls Darth Vaders "can't shoot a couple of rebels to save Death Star, suckers" squadron "Black Squadron" but IIRC that name never made it into Disney canon.
This convention also made it into New Disney canon, with the Admiral Rae's Sapphire Squadron from Rise of the Empire.
Evoking Wing Commander series Broadswords, Rapiers etc..., some squadrons were named after Melee weapons:
Saber, Dagger Flight and Cutlass as well as generic Blade Flight show that the spirit of Wing Commander is alive and well. Second Death Star had a Scythe squadron, because nothing beats an agricultural implement in a sturdy farmboy's hands.
EU also has both Scimitar squadron from trading card game, not to be confused with even more confusing Scimitar Flight (which to confuse matters more, was part of 77th Air Wing's Sword Squadron. You're welcome) from Star Wars Insider article.
Some names were cool yet funcional
Grand Admiral Thrawn had a Cloak squadron, because
he was a fan of Deathly Hallows like Dumbledore they were using cloaking technology in violation of Khitomir accords.
As Richard's comment noted, a very good list of known Imperial squadrons can be found on Wookiepedia.