To customize the look of the subscription widget, you can add the following CSS to your theme stylesheet, or to your custom CSS editor under Appearance > Edit CSS in your dashboard:
#sidebar .jetpack_subscription_widget input[type="submit"]
.buttons a{
margin-right:30px;
}
#sidebar .jetpack_subscription_widget input[type="submit"] {
background-image: linear-gradient(top, #b5e0f7 0%, #76c7f1 100%);
background-image: -o-linear-gradient(top, #b5e0f7 0%, #76c7f1 100%);
background-image: -moz-linear-gradient(top, #b5e0f7 0%, #76c7f1 100%);
background-image: -webkit-linear-gradient(top, #b5e0f7 0%, #76c7f1 100%);
background-image: -ms-linear-gradient(top, #b5e0f7 0%, #76c7f1 100%);
background-image: -webkit-gradient(
linear,
left top,
left bottom,
color-stop(0, #b5e0f7),
color-stop(1, #76c7f1)
);
border:1px solid #1172c1;
color:#1172c1 !important;
display:inline-block;
height:32px;
font:13px/32px 'PTSansBold', arial, helvetica, sans-serif;
text-transform:uppercase;
text-align:center;
text-shadow:0 1px 0 #fff;
padding:0 20px;
-webkit-border-radius: 2px;
-moz-border-radius: 2px;
border-radius: 2px;
-webkit-box-shadow: 0 1px 1px rgba(0,0,0,0.2);
-moz-box-shadow: 0 1px 1px rgba(0,0,0,0.2);
box-shadow: 0 1px 1px rgba(0,0,0,0.2);
}
#sidebar .jetpack_subscription_widget input[type="submit"]:hover{
color:#1172c1 !important;
background-image: linear-gradient(top, #76c7f1 0%, #b5e0f7 100%);
background-image: -o-linear-gradient(top, #76c7f1 0%, #b5e0f7 100%);
background-image: -moz-linear-gradient(top, #76c7f1 0%, #b5e0f7 100%);
background-image: -webkit-linear-gradient(top, #76c7f1 0%, #b5e0f7 100%);
background-image: -ms-linear-gradient(top, #76c7f1 0%, #b5e0f7 100%);
background-image: -webkit-gradient(
linear,
left top,
left bottom,
color-stop(0, #76c7f1),
color-stop(1, #b5e0f7)
);
border:1px solid #1172c1;
}
This CSS actually already exists in your theme stylesheet, but you need to apply it to the Subscription button as well. I targeted that button with the following CSS:
#sidebar .jetpack_subscription_widget input[type="submit"]
