native/libawt_lwawt/awt/CSystemColors.

    if (@available(macOS 10.14, *)) {
        sColors[java_awt_SystemColor_CONTROL_HIGHLIGHT] = [NSColor selectedContentBackgroundColor];
    } else {
        sColors[java_awt_SystemColor_CONTROL_HIGHLIGHT] = [NSColor alternateSelectedControlColor];
    }

After JDK-8317970 is integrated to make macOS 11 the minimum this check is obsolete and can be removed.