A few things can be helpful for you when using Markdown Block in Squarespace.
Notes
Change Markdown Block Color
Add this CSS
.markdown-block {
background: gray;
}
Center Text Markdown
Use this CSS
.markdown-block {
text-align: center;
}
Center Header
Use this CSS
.markdown-block h1 {
text-align: center;
}
.markdown-block h2 {
text-align: center;
}
.markdown-block h3 {
text-align: center;
}
.markdown-block h4 {
text-align: center;
}
.markdown-block h5 {
text-align: center;
}
.markdown-block h6 {
text-align: center;
}
Markdown Font Color
When typing text in Markdown, use this format
Hey, <span style="color:red;font-size:20px;text-decoration:underline;">you know how</span> I'm, like, always trying to save the planet? Here's my chance

Markdown Box Around Text
Use this CSS
.markdown-block {
background: #f1f2f4;
border-color: red;
border-width: 2px;
border-style: solid;
padding-top: 10px;
padding-bottom: 20px;
padding-left: 20px;
padding-right: 20px;
}

Markdown Open Link in New Tab
You can use 2 ways
Way 1. Use this format when typing link
<a href="https://google.com" target="_blank">Text link</a>

Way 2. Use jQuery
First, typing text link in Markdown Block. You can follow below guide (or see this)

Next, add this code to Home > Settings > Advanced > Code Injection > Header (or Page Settings > Advanced > Header)
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.4.1/jquery.min.js"></script>
<script>
$(document).ready(function () {
$('.markdown-block a').attr('target','_blank');
});
</script>

Markdown Center Image
First, to insert images to Markdown, follow this guide.

Next, to center image in Markdown, add this CSS
.markdown-block img {
display: block;
margin: 0 auto;
}
Strike Through Text in Markdown
To create strike through text, type text in this format
here is <span style="text-decoration:line-through;">strike text</span>

Increase Font Size in Markdown
Use this format
here is font with <span style="font-size:50px;">big size</span>

Underline Text in Markdown
Use this format
<span style="text-decoration:underline;">underline text</span> markdown

Make a Table in Markdown
With Business Plan or higher, Use this tool.
With Personal Plan, you can use this code, or Google: HTML table 😀
<div style="overflow-x:auto;">
<table>
<tr>
<th>First Name</th>
<th>Last Name</th>
<th>Points</th>
<th>Points</th>
</tr>
<tr>
<td>Jill</td>
<td>Smith</td>
<td>50</td>
<td>50</td>
</tr>
<tr>
<td>Eve</td>
<td>Jackson</td>
<td>94</td>
<td>94</td>
</tr>
<tr>
<td>Adam</td>
<td>Johnson</td>
<td>67</td>
<td>67</td>
</tr>
</table>
</div>
If you have any questions, just click in button below!
Hello Tuan,
this is Cris from Switzerland. I have been trying to change the color of an hypelink underline in a markdown block, but with no success. The only thing I have been able to do is changing the color of both, text and underline:
#block-yui_3_17_2_1_1620830017300_7249 h3 a{
color: #B2C332!important;
}
But how can I address the color of only the underline?
Thank you,
cris