How to change color of the rank titles?

Hi,
You can type html colour tags for each individual title in the PlayerRanks.json config file, like this

"Title": "<color=#d4d3d3>Killer</color>"

or, if you want all titles to be the same colour,
you can add the opening tag to TitleStart and the closing tag to Title End, like this

    "TitleStart": "<color=#d11d38>",
    "TitleEnd": "</color>",