If you want to change the default “plain text” color: Settings > Style Configurator > Language: Global Styles > Style: Default Style > Colour Style: Foreground Colour ☐
For syntax highlighting, you can use the same dialog box, selecting the appropriate Language choice (ie, which programming language you want the change to apply to) and appropriate Style selection (ie, which specific item in that particular language) for the color you want to change. For example, if you wanted your HTML syntax highlighting to use light gray for <!-- comments --> rather than dark green, you would pick Language: HTML > Style: COMMENT > Colour Style: Foreground Colour ☐ , and choose a light gray.