Personal advice on using greyscale and colorizing after, versus painting once in true color.
The gradient on the left was a black and white gradient. I used several hue, variation and selective color tricks to colorize it. The gradient on the right is just painted using different hand picked colors.
The difference between the two are the terminators; where one color transitions into the next. Whenever Photoshop does the coloring, the transition is less saturated and its always an exact blend between the two colors.
Some people use gradient maps, some use color overlay layers and some use selective color. Whatever the process, textures that were made in greyscale method are rarely as vivid as textures painted in true color and its because of the transitions between colors.
This is a general statement because just painting in color does not mean you will automatically have better textures, but it is a good practice to learn how to paint in true color.