In Generation IV
HM05 Defog

TMs and HMs that teach Water-type moves are supposed to be a deep blue. While Flying-type TMs and HMs are normally colored a lighter blue, the HM that teaches Defog is colored a deeper blue, as if it teaches a Water-type move.
In Generation V
TM67 Retaliate
In Japanese versions of Pokémon Black and White, Retaliate is a Normal-type move, but its TM sprite is shown as a Dark-type move. This has been fixed in other language versions of those games.TM94 Rock Smash
In Pokémon Black and White, Rock Smash is a Fighting-type move, but its TM sprite is shown as a Rock-type move. This has not been fixed in newer releases.In Generation VII
__Flying-type_TMs_(TM14_Fly_and_TM50_Roost)_"> Flying-type TMs (TM14 Fly and TM50 Roost)

Since Pokémon FireRed and LeafGreen introduced icons for items to the mainline Pokémon series, TMs have been represented by a disc (colored according to the move's type); HMs use a variant of the same design with an oval cutout in the topmost part of the disc. In Pokémon: Let's Go, Pikachu! and Let's Go, Eevee!, there are no HMs (since they are functionally replaced by Secret Techniques), so even TM47 (Surf), which teaches a former HM move, uses the TM icon.
However, in Pokémon: Let's Go, Pikachu! and Let's Go, Eevee! 1.0.2 (and likely in earlier versions), the icon for Flying-type TMs has the oval cutout that is otherwise unique to HMs. This affects TM14 (Fly) and TM50 (Roost). Note that although Fly is a former HM move, Roost has never been a HM move, or even a field move, in any of the previous games.