Decolorization will turn to gray mode, and there is only one brightness channel, that is, a single channel, so there will be no color.

Two methods:

1, use the black and white tool (Alt+Shift+Ctrl+B)

It is recommended to use the black and white tool, because it can manually and selectively adjust the gray levels of different colors according to the color structure of the picture. Moreover, it is still RGB mode (color mode) after conversion, and there is no need to save one step when converting to RGB.

2. Turn to RGB after ash removal (ash removal is unified according to the empirical formula, and sometimes some bright colors will turn gray after turning to black and white, which is not white enough).