Sure,
You can create a new theme component, attach it to your theme, and add the following CSS:
.custom-search-banner-wrap {
h1 {
color: blue; /* headline*/
&+p {
color: red; /* subhead */
}
}
.search-menu {
.btn.search-icon.has-search-button-text {
.d-icon {
color: orange; /* search button icon */
}
.d-button-label {
color: orange; /* search button text */
}
}
}
}
Does it help?