It took us hours to find it but here is the way to change the hoover color, not sure about the button color:
It appears you can change the hover colors here for the currency and add to cart buttons.
In your store data structure through cpanel legacy file manager or what ever manager you use go to
storefront>view>default_html5>stylesheet>style.css
The changes for the hover color is done in the style.css file.
(you have to change your html codes to rgb, then the last part a is a transparency value - here I changed the original values to a grey color)
code:
.headerdetails ul.nav.language li.dropdown:hover,
.headerdetails ul.nav.topcart li.dropdown:hover {
border-color: rgba(150, 155, 164, 0.6);
outline: 0;
outline: thin dotted \9; /* IE6-9 */
-webkit-box-shadow: inset 0 1px 1px rgba(0, 0, 0, 0.075), 0 0 8px rgba(150, 155, 164, 0.6);
-moz-box-shadow: inset 0 1px 1px rgba(0, 0, 0, 0.075), 0 0 8px rgba(150, 155, 164, 0.6);
box-shadow: inset 0 1px 1px rgba(0, 0, 0, 0.075), 0 0 8px rgba(150, 155, 164, 0.6);
Hope this helps as it took us hours to find it. Ugh! What a pain that was!
Kimberly