That won't conflict if your Bootstrap 4 template has properly set the colors to :root. See the CSS below
Code:
.cb_template .btn-dark:focus {
/* workaround to Bootstrap 3.0 styling */
color: #fff;
color: var(--white, #fff);
background-color: #343a40;
background-color: var(--dark, #343a40);
}
Line 250 is background-color: #343a40; which is just a fallback that'll only apply if the variable doesn't exist or the browser doesn't support var function (all modern browsers do). Otherwise it'll use the --dark var that Bootstrap 4 sets to :root. If your Joomla template is loading Bootstrap 4 without setting the color variables to :root then it's using Bootstrap 4 CSS wrong and suggest contacting the template developer.
You can also use CB Template Changer to generate a new template with your colors and leave Bootstrap 4 disabled in CB > Configuration > Integrations.
krileon
