Step 1: Use the lasso tool or pen tool in the toolbox to circle the part of the text that needs to be changed in color as the selection.

Step 2: Set the foreground color [text color to be changed] through the PS color picker.

Step 3: If the word needs to be changed into a gradient color, fill it with the gradient tool and adjust the gradient before filling. If the words are only changed to simple colors, they can be filled directly with the paint bucket tool.