1. First, open the quick PDF editor, click Open in the upper left corner to add the file whose color needs to be changed, or click Open File to add.

2. Secondly, after the file is added, click Tools, Labeling and Marking, and Highlight Text Tool in the menu bar above, and select the color you want to mark. Then find the red mark and double-click it.

3. Then, after selecting the green color to be marked, we select the text to be marked, and directly pull the segment to be marked to complete the color coverage.

4. Click the "File" button in the upper left corner, and select the "Save" or "Save As" button in the expanded list to complete the modification of the tag color.