Just add !important; in color: #FFD180 in the hover part of your CSS.
.btn-custom:hover, .btn-custom:focus, .btn-custom:active, .btn-custom.active, .open>.dropdown-toggle.btn-custom { color: #FFD180 !important; background-color: #837171; border-color: #837171; }
Edit: color (# 333) probably comes from this line in bootstrap.min.css
.dropdown-toggle.btn-default{color:#333;background-color:#e6e6e6;border-color:#adadad}
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