I was able to solve this eventually by looking at the code using the developer tools on the web browser. There are two pieces of code you need to put into the theme's XML document (path: alfresco-community\tomcat\webapps\share\WEB-INF\classes\alfresco\site-data\themes\"YOUR_THEME").
1) When changing the title's font color for created sites, put this piece of code anywhere in between the <less-variables> ... </less-variables> tags within the XML document:
@link-title-font-color: your color; (ex: "@link-title-font-color: #FFFFFF;" for white font)
2) When changing the title's font color for the home dashboard and other pages that are not created sites, put this code in between the <less-variables> ... </less-variables> tags within the XML document:
.alfresco-share h1.alfresco-header-Title .alfresco-header-Title__text.has-max-width
color: your color !important; (ex: "color: #000000 !important;" for black font)
NOTE: the "....alfresco-header-Title__text.has-max-width" part has two underline characters (i.e. '_'), not just one. Also, the only part of the code that you need to change is the 'your color' part. Finally, don't forget the "!important" tag after your color because that allows your piece of code to override the original color.
Hope this helps anyone who may have had the same problems as me.