Insert a filter layer with Desaturate filter on the top. Then you can toggle the visibility of that layer to view in black and white.
How do I convert to grayscale in Krita?
The default shortcut for this filter is Ctrl + Shift + U . This will turn colors to gray using the HSL model.
Why is Krita black and white?
You are either on a black&white layer (for example you’re on a mask, or Fill layer, or Filter Layer etc., not a normal layer), or the image you’re working on is in the GRAYA color space. Please attach the screenshot of your whole Krita window if you’re not sure about either and you don’t know how to fix it.
How do I change from grayscale to RGB in Krita?
If it says something about grayscale, then the colorspace of the image is grayscale. To fix that go to menu Image->Convert Image Colorspace... and select RGB.