Fill w/foreground color

`Shift` + `Backspace`

All hotkeys for Krita Painting 3 (Windows)

Painting Eraser mode	`E`
Painting New paint layer	`Insert`
Painting Clear	`Delete`
Painting Fill w/background color	`Backspace`
Painting Pick layer	`R`
Painting Activate next layer	`Page up`
Painting Activate previous layer	`page down`
Painting Gradient tool	`G`
Painting Move tool	`T`
Painting Multibrush	`Q`
Painting Color pick	`P`
Painting Merge down	`Ctrl` + `E`
Painting Rect. selection	`Ctrl` + `R`
Painting Transform tool	`Ctrl` + `T`
Painting HSV/HSL adjust	`Ctrl` + `U`
Painting Invert	`Ctrl` + `I`
Painting Duplicate layer	`Ctrl` + `J`
Painting Levels	`Ctrl` + `L`
Painting Display selection	`Ctrl` + `H`
Painting Wrap around mode	`W`
Painting Switch to previous preset	`/`
Set/Reset Reset picker - BW	`D`
Set/Reset Palette	`F`
Set/Reset Elliptical selection	`J`
Set/Reset Decrease brush size	`[`
Set/Reset Increase brush size	`]`
Set/Reset Previous fav preset	`,`
Set/Reset Next fav preset	`.`
Set/Reset Switch to previous preset	`/`
General Select all	`Ctrl` + `A`
General Undo	`Ctrl` + `Z`
General Redo	`Shift` + `Ctrl` + `Z`
General Open	`Ctrl` + `O`
General Deselect	`Shift` + `Ctrl` + `D`
General Save incremental backup	`F4`
General Export	`F5`
General Print	`Ctrl` + `P`
General Cut	`Ctrl` + `X` / `Shift` + `Delete`
General Save as	`Shift` + `Ctrl` + `S`
General Quit	`Ctrl` + `Q`
General Save incremental	`Alt` + `Ctrl` + `S`
General Close	`Ctrl` + `W`
General Copy	`Alt` + `Ctrl` + `J` / `Ctrl` + `C`
General help	`F1`
General Copy merged	`Shift` + `Ctrl` + `C`
General Save	`Ctrl` + `S`
General Paste	`Ctrl` + `V`
General New	`Ctrl` + `N`
Others What's this	`Shift` + `F1`
Others Color selector	`Shift` + `I`
Others Set mirror axis	`Shift` + `R`
Others Hide tip toolbar	`Shift` + `H`
Others Show dockers	`Shift` + `B`
Others Minimal shade selector	`Shift` + `N`
Others Mypaint shade selector	`Shift` + `M`
Others Undo polygon selection points	`Shift` + `Z`
Others Flatten image	`Shift` + `Ctrl` + `E`
Others Total refresh	`Shift` + `Ctrl` + `R`
Others Full screen mode	`Shift` + `Ctrl` + `F`
Others Desaturate	`Shift` + `Ctrl` + `U`
Others Invert selection	`Shift` + `Ctrl` + `I`
Others Cut sel to layer	`Shift` + `Ctrl` + `J`
Others Deselect	`Shift` + `Ctrl` + `A`
Zoom Zoom out	`Ctrl` + `-` / `-`
Zoom Zoom in	`Ctrl` + `+` / `=`
Zoom Zoom to fit width	`3`
Zoom Zoom to fit	`2`
Zoom Zoom 1:1	`1`
Zoom Zoom 1:1	`0`
Rotate
Rotate Rotate right	`Ctrl` + `]`
Rotate Reset canvas view	`Ctrl` + `'`
Rotate Rotate left	`Ctrl` + `[`
Rotate Rotate reset	`5`
Rotate Rotate right	`6`
Rotate Rotate left	`4`
Canvas Canvas only mode	`Tab`
Canvas Toggle full screen	`F11`
Pan Pan left	`Left arrow`
Pan Pan right	`Right arrow`
Pan Pan up	`Up arrow`
Pan Pan down	`Down arrow`
Color
Color Decrease opacity	`I`
Color Fill w/foreground color	`Shift` + `Backspace`
Color Darken color	`K`
Color Brush tool	`B`
Color Show common color	`C`
Color Lighten color	`L`
Color Increase opacity	`O`
Color Color balance	`Ctrl` + `B`
Color Swap fg/bg colors	`X`
Color Show color history	`H`