Yep, the easiest way to do this at the moment is to simply include a style block in the HTML of your template, like so:
<style>
button { background-color: red; margin-right: 10px;}
</style>
etc.
Also, if you want to individually style buttons, just include an id on each button, then target it with your style block. Like so:
<style>
#power-button { background-color: red; }
#reset-button { background-color: yellow; }
</style>
<button id="power-button">Power</button>
<button id="reset-button">Reset</button>
And so forth...