Little confused which page you wanted this hover effect but try this:
.wp-show-posts-image .wp-post-image img {
filter: grayscale(100%);
-webkit-filter: grayscale(100%);
}
.wp-show-posts-image .wp-post-image img:hover {
filter: none;
-webkit-filter: grayscale(0);
}
Let me know 🙂
