A better approach is to paint white on a separate layer and use a blend mode that preserves texture, rather than Multiply. Multiply darkens, which is why your cabinets turn gray.

Try this:

1. Select the cabinet area.
2. Add a new layer above the photo.
3. Set that layer’s blend mode to a texture-preserving mode such as Grain Merge (or the closest equivalent available in Photoshop).
4. Paint white onto that layer over the cabinets.
5. Adjust the layer opacity until the result looks like painted wood rather than flat solid color.

Also check your paint/tool opacity and make sure it’s set to 100% if you want the white to apply fully; low opacity can also make the result look gray.

The key idea is: use a separate white paint layer plus blend mode and opacity control to keep the cabinet grain visible.