I just want to change the colour of the donate button- not the drop down menu

[GinaB2]

I have added this code so that the donate button will be a different colour. However it has changed the colour of the last menu item on my dropdown menu for web and mobile. Can you help me change the code so that it is only the donate button that is green. 

This was the code used: 

.header .header__inline-menu .list-menu > li:last-child > a{
background: green;
border-radius: 40px;
text-decoration: none !important;
padding-left: 30px;
padding-right: 30px;
color: #fff!important;
}
.header .header__inline-menu .list-menu > li:last-child > a span {
text-decoration: none;
color: #fff;
}
.menu-drawer__navigation .menu-drawer__menu > li:last-child {
padding: 0 3.2rem;
}
.menu-drawer__navigation .menu-drawer__menu > li:last-child a{
background: green;
border-radius: 40px;
color: #fff!important;
justify-content: center;
}

[GinaB2]

Thank you for your response. 

The donate is just a menu item- could you point me in the right direction of where to add the class? 

[GinaB2]

I cant find it- I spend my day rescuing dogs, so not great with coding! haha

Thank you for your help- I will have to keep looking- it must be there somewhere 🙂