I am a novice and i am having a challenge trying to change the mobile drop down menus colour, i have found the code that needs changing to make it red using inspector, i then have found the relevant code in the bootstrap.min.css and made the change but upon saving it does not do anything. could anyone let me know what i am doing wrong or what could be stopping it from working. code below

.dropdown-menu > li > a {
display: block;
padding: 3px 20px;
clear: both;
font-weight: 400;
line-height: 1.42857143;
color: #ff0000;
white-space: nowrap
}