Hi,
To change the style of the messages you can use the Custom CSS tool:
.msg {
padding: 1.1333333333rem 2.2666666667rem;
}
.msg--highlight {
background-color: #F7F5EA;
}
.msg--info {
background: #F2F9FF;
}
.msg--success {
background: #F7FBF6;
}
.msg--warning {
background: #FFF3F3;
color: #A94442;
}
The AMP footer can be edited via its settings (Site Settings → Advanced options → AMP )