Thank you!
Did it with the following CSS:
.ui-fileupload-buttonbar {
background-color: #f3f5f7;
}
.ui-fileupload-buttonbar > .ui-fileupload-choose {
font-size: 1.0625rem;
background-color: #ff6d41;
height: 2.1875rem;
}
.ui-fileupload .ui-button .ui-button-text {
line-height: 2.1875rem;
}