the h1 as you want it, is styled by .singular .entry-title
:
.singular .entry-title {
color: #000;
font-size: 36px;
font-weight: bold;
line-height: 48px;
}
obviously the page with sidebar is missing the .singular
body class;
copy the style of .singular .entry-title
and create the same for .page-template-sidebar-page-php .entry-title
in style.css of the child theme:
.page-template-sidebar-page-php .entry-title {
color: #52587b;
font-size: 36px;
font-weight: bold;
line-height: 48px;
}
a tool such as Firefox’ web developer add-on (or any similar browser inspection tool) is very useful in dealing with these kind of fundamental formatting problems.