Change font colour in site title

You need a “child theme”

style.css for it –

/*
Theme Name: Corporate-lite Child
Description: Child Theme of corporate-lite
Author: Vlad
Template: corporate-lite
*/

@import url(“../corporate-lite/style.css”);

.header .logo h1{ color:#abcdef;}

Or just change style.css in theme, but you will lost changes after theme update

Or use Simple Custom CSS and JS module for it.

Or for logo – try create custom css in footer and paste it:

.header .logo h1{ display:none;}
.header {
    background: url("https://assets.onestore.ms/cdnfiles/onestorerolling-1604-22001/shell/v3/images/logo/microsoft.png") no-repeat scroll left top rgba(0, 0, 0, 0);
}