To edit the fonts and colors of the slider, go to Theme > Customize > Advanced > click on "Links" to expand the dropdown > scroll down until you find the Slider section.
You can easily show/hide the content, post date, snippet, etc, on the slider. Go to Layout > open the "Post Slider" widget > edit the settings (number of posts, show/hide the post content, date, etc).
Here's the code for the slider, in case the widget is deleted (add it to a HTML/JavaScript widget in Layout):
<script type="text/javascript">
var numposts = 4;
var showpostcontent = true;
var showpostdate = false;
var showpostsummary = false;
var numchars = 1;
var displaymore = false;
var buttontext = "read more";
</script>
<script type="text/javascript" src="/feeds/posts/default/?published&alt=json-in-script&callback=postslider"></script>
Display posts from a label
Go to your blog dashboard > Layout > open the "Post Slider" widget > replace this:
<script type="text/javascript" src="/feeds/posts/default/?published&alt=json-in-script&callback=postslider"></script>
With this:
<script type="text/javascript" src="/feeds/posts/default/-/Label Name?published&alt=json-in-script&callback=postslider"></script>
Replace Label Name with the name of the label you want to display posts from.
Important: Blogger's labels are case sensistive, so the label has to be written exactly the same way you've written it in your posts, otherwise no posts will be displayed.
Slider not working
- Go to your blog dashboard > Settings and check if your blog is set to Private. Your blog has to be public - the widget uses the blog feed to display posts and when the blog is private, the feed is inactive.
- If your blog is Public, but the widget is still not showing up, go to your blog dashboard > Settings > Other and make sure "Allow Blog Feed" is set to "Full" or "Until Jump Break". If it's not set to Full, the widget can't display posts.
- If you're displaying featured posts instead of recent posts, double-check if the label is written the same way in the code as it is in your post. Blogger's labels are case sensisitive; for example, if the label is written as Lifestyle in your post, but as lifestyle in the code, Blogger will consider them two different label pages.
Blurry images
To avoid blurry images in the slider, the first image in your post should be at least 1200px wide (the rest can be smaller). And select "Original" size * - Blogger displays the images in small format unless you select another option.
* To select "Original" size, open your post in the editor > click on the image > click on the "Image size" icon (fourth icon from left to right) > select "Original" from the dropdown.