Mermaid ER diagram styling

I want to draw an ER diagram with Mermaid. But I can't find out how to style the box to make it with different colors.

I know it's possible to set the theme color, but I can't do it to each box. I've tried different syntaxes and found some information on the offical documentation, but I can't figure out how to use them.official docs
I want to make it like this:example

The Mermaid syntax does not currently support custom colors for ER diagrams without custom CSS.

There's an open issue about this, and this comment provides a solution when you can control the diagram source and the CSS for the theme: https://github.com/mermaid-js/mermaid/issues/2673#issuecomment-1522470695

Here is an example (Mermaid Live link)

Note, that in the live link, I put the init directly in the code rather than the config. This is because it makes it easier if I want to copy it somewhere else.

%%{init: {
  "theme": "default",
  "themeCSS": [
    ".er.relationshipLabel { fill: black; }", 
    ".er.relationshipLabelBox { fill: white; }", 
    ".er.entityBox { fill: lightgray; }",
    "[id^=entity-some] .er.entityBox { fill: lightgreen;} ",
    "[id^=entity-mytable] .er.entityBox { fill: powderblue;} ",
    "[id^=entity-anothertable] .er.entityBox { fill: pink;} "
    ]
}}%%

The first three settings set the default css, the last three are specific to a table using a pattern.

Note that when testing in Mermaid Live and maybe some other implementations, you need to prefix the table name/pattern with entity-, but in some other implementations (e.g. Gitlab), you would need to remove that prefix to get it to work.