Convert to black and white
Monochrome is a switch in the Profile section. It turns the whole photo gray after your other edits, and your colors are kept underneath, so you can switch it off again.
Convert a photo
Section titled “Convert a photo”- Open Profile in the left column.
- Turn on Monochrome.

Monochrome is global. It applies to the whole photo, not to a single layer.
Shape the tones by color
Section titled “Shape the tones by color”A plain conversion gives every color its natural brightness. To make a blue sky darker or green foliage lighter, use the Color Adjust section:
- With Monochrome on, the section is titled Color Adjust · Luminosity and shows only Luma Shift. Hue and saturation can’t show in a gray image.
- Click the color picker, then click a color in the photo, or drag across an area, to add an edit that selects it.
- Drag Luma Shift to darken (negative) or lighten (positive) everything that color selects.

The brightness change happens before the gray conversion, so it carries through. Color Adjust belongs to a layer, so a layer with a mask can darken just the sky.
Technical details: how the conversion works
The conversion keeps each pixel’s perceptual lightness (Oklab L) and drops its color. The result is a true neutral gray in linear light, with no per-color mix of its own: the mix is what Luma Shift does, earlier in the chain. Monochrome runs after the layers and before the crop, the vignette and the look, so a vignette darkens the gray image and a look tints it.