Here are LOTS of ideas I thought.

1. Reverse lockholes: A door with pink lockholes that requires POSITIVE keys to open, but instead of SUBTRACTING the key of the following color it ADDS the key of the following color.
1. Its negative variation is a door with cyan lockholes, which requires NEGATIVE keys and SUBTRACTS keys.
2. Convert keys: A key object that convert all the key of one color to another. For example, picking a pink -> cyan Convert key while you have 2 pink keys and 3 cyan keys will make it become 0 pink keys and 5 cyan keys.
3. Keepable keys and doors: A key or door that can be not interacted if a certain button is pressed. If it is a key the player can pass through without collecting it, while if it is a door it will not be opened and can blocks player.
4.  Variable keys and doors: A key or door that can changes its key amount in a certain situation, or changes its color, or even appearing and disappearing, and many more.
   1. Its possibility is endless!
5. Tricolored doors and doors of more colors: Similar to Bicolored doors, it will modify the key count of  ALL the colors in its outer border.
6. Simple doors: A door that can only be opened if the key count of the following color is not a complex number. For example, a Simple door can be opened with 0, 3, -2, 5i or -1i keys, but not a complex number of keys like 1+2i.
   1. Its variation is Complex door, which can only be opened by a complex number of keys.
7. Unstable Glitch keys: A new key type that can changes its color even after collected, and it will treads as the color of the last door opened.
8. Dispel aura effect: A weird aura effect that make the affected doors cost nothing after opened. The base cost of the door itself still need to be afford before it can be opened.
9. EDIT: 2024/07/13 Glass Doors: A door variant that has transparent looking, when you met its requirement, you break it as normal and cost your keys normally when you touch it, but if you do not met its requirement, you will break it without costing anything. For example, touching a Glass Orange 6 door when you have 6 or more Orange keys will open it normally and cost you 6 Orange keys, but if you have 5 or less Orange keys you will break it too and let your Orange keys unmodified.
   1. Those doors use the glass-breaking sound exists in I Wanna KeyPick 100, played when you open a door that costs negative number of keys.
10. Silver Keys & Doors: A third key and door type that have glowing animation as Master (Gold) and Pure (Platinum) keys. The Silver Doors can be opened by Master Key charges but can not be cursed, as Master Doors can be cursed but can not be opened by Master Key charges, and Pure Doors can not become both.

Also see: 

• I have several ideas for door properties (spoilers for pretty much the whole game) - I Wanna Lockpick community - itch.io
• Idea: Partial Doors - I Wanna Lockpick community - itch.io
• Idea: Switch Keys/Doors - I Wanna Lockpick community - itch.io
• Idea: Absorbtion keys - I Wanna Lockpick community - itch.io
• Idea: Multiplying Keys - I Wanna Lockpick community - itch.io

 More ideas for the PILE:

Shadow Doors/Ghost Doors.

A incorporeal transluscent door type that doesn't have collision. (Basically being walkthrough if you don't meet the condition and dissapearing after the keys are spent. This could be paired with any other door type, and could lead to intresting dynamics.

Edit: holy crap I predicted the name. dang. Well this is now unoriginal. Big sad :( 

Skeleton Keys. 

A master-esque key that turns the door it touches into a ghost door. Negative versions turn a door back.

Badges.

Gold, pure, and skeleton stickers that are placed on doors, functioning as a immunity to those door types. Essentially a extra outside color without the cost swap.

Minilocks.

These would be doors that effectively would function as keys, being put in a 1-10 door inventory when picked up. They could be stacked and would jam you from using master keys, because they would automatically trigger when their conditions are met, being resolved from top to bottom, left to right. I hope you aren't carrying any brown keys. 

Quantum Doors.

Doors with a dotted gray line between them. When one of them disappears or is cloned, the other is as well. Effectively being a minor Linked Door. When one is salvaged, both of them appear in the same spot they were relative to each other. A Quantum Door would also count as one door for the purpose of all auras.

Updated a new idea, thank for Balatro, a rouge-like card game.