Hello,

1. You can try to alter login-modal-template.php file located in >> \wp-content\plugins\eltdf-membership\widgets\login-widget\templates\login-modal-template.php

2. Please note that you can go to Elated Options >> General >> and then navigate to First main color and choose the most dominant theme color.

For some other elements, you can choose desired color through Elated Options, within shortcode settings or with some custom css (in that case we can assist you with that).

You can go to Elated Options >> Header >> 1st/2nd level Menu

Then add this css below in Appearance >> Customize >> Additional CSS field:

.eltdf-drop-down .second .inner {
    border-color: red;
}
#eltdf-back-to-top>span:hover {
    background-color: red;
}