Yes you can add something like this in your Responsive section (near the bottom of the CSS file) –
.front-page-1 .image-section h4 {
font-size: 42px;
}
That controls the front-page-1 widget.
If you want to control all of the Home Page widget titles, then you can add something like this –
.image-section h4,
.solid-section h4 {
font-size: 42px;
}
Let me know if this helps.