The submit button color comes from the theme options > basic styling. Your primary color.
The hover is your lighter primary color. If you would like to change without changing your theme options you can use css like this:
.contactform .kad-btn-primary {
background: blue;
}The form is on the right by default. You can move it left with this css:
@media (min-width: 992px){
.page-template-page-contact-php div#main {
float: right;
}
}Kadence Themes