Create custom image when SHIFT key is pressed?

Is this something to create in CorelDRAW or FontForge?

Seeking advice to create specific key sequence, mapped to a custom graphic.

1) Custom glyphs will  be designed for the SHIFT, ALT, and CTRL keys are pressed.
        SHIFT + A = (my custom glyph 1)
        CTRL + A = (my custom glyph 2)
        ALT + A = (my custom glyph 3)

2) Also is there a way to make a custom font graphic full color?
The graphic needs to be a specific size compared to the font letters.

I'm not creating a complete custom font (yet) so I need to use an existing font like Calabri and add the custom glyphs and key maps to it.