Is it possible to change the size, color and location of the Prompt for User Input window?

[hello]

change size, color of a Prompt

for size and color, not that I'm aware of.
The only alternative I know so far is to style a HTML prompt using CSS.

position

there' s a thread here about how to position it:

Controlling The Position of User-Prompt Windows on The Screen

There is a way to do this besides using AppleScript, but it's not obvious or enabled by default. The easiest way I've found to do so with KM actions requires that an alias to the Keyboard Maestro Engine (found in the Keyboard Maestro app package at /Keyboard Maestro.app/Contents/MacOS/Keyboard Maestro Engine.app be added to the Applications folder. Once that's done, you can use KM's Manipulate a Window action to center KM prompts and alerts like this: Center Keyboard Maestro Prompts and Alerts.…