In posts.css, you want to change this:
.hentry:hover .thumb-shadow {
background-position: center bottom;
}
to this:
.hentry .thumb-shadow {
background-position: center bottom;
}
(i.e., you just remove the :hover from after .hentry. This will display the shadow under the thumbnail.
Then, also in posts.css, you want to comment out (or remove entirely) this section:
.post-thumb img.img_grayscale {
filter: grayscale(100%); /* Current draft standard */
-ms-filter: grayscale(100%);
-o-filter: grayscale(100%); /* opera */
filter: url("%tpldir%/images/gray-filter.svg#grayscale"); /* Firefox */
filter: gray; /* IE */
-webkit-filter: grayscale(1); /* Old WebKit */
-webkit-filter: grayscale(100%); /* New WebKit */
}
What this does is set the top layer of the thumbnail (the img_grayscale layer) to gray, so we’ll just comment it out so the top image is color.
That is, the thumbnail is comprised of two identical images, one on top of another. The top layer is set to gray using the CSS above, and the opacity is initialized to 1, while the bottom image remains color, but the opacity is set to 0 so you can’t see it. When the mouse moves into the area of the post, there’s a JavaScript event handler which gradually changes the opacity of the top, gray image from 1 to 0 (making it clear), and the opacity of the bottom, color layer from 0 to 1 (so it becomes visible).
The only thing left is to add a line to your JQuery code in the Bottom field of your Head section (your code area is growing quite large, now). Add this line before the ending brace of the ready function:
$('.hentry').off("hover");
What this does is remove the previously mentioned event handler for when the mouse enters the post area, so it doesn’t try to animate the thumbnail transition.