Answer :
Just add this code to your text area and you are ready to customize from first moment -
<style>
.sfc-action-button {
color: #ffffff !important;
font-size: 26px !important;
height: 36px !important;
background-color: #858585!important;
background-image: none !important;
}
</style>
In case, just in case, If HTML Sensitization is enabled by your admin - You are bit unlucky. Still you can do a few stuffs using JavaScript codes. A Small Example code here-$(".sfc-action-button").css({
"width":"600 px",
"font-size": "200%"});