Hi There,
As you are using it now you can add a inline styling to each h1 headline.
Please follow this example:
<h2><span style="color: #808080; font-size: 300% ">Custom<strong> Menu Plans</strong></span></h2>
This code applies to a h1 h2 h3 just applied the same way and adjust the value 300% to the desired size.
If you use a Custom Headline instead you can add the code below in the Style Box of your Custom Headline Element.
font-size: 400%;
Please see img attached.
Hope it helps,
Joao