How do you style a external svg with css

Is it possible to style an external .svg with css like you would with text? What am I missing? My mark up and css looks like this:

<style type="text/css">
#ob {
    color: blue;
}

svg {
    fill: currentColor;
}   


<object id="ob" type="image/svg+xml" data="czo_svg_icons/czo_extra_closed.svg">Your browser does not support SVG</object>

If you include your svg image by referencing an external file, like you do with the object tag, the elements in the svg image are not included to your main documents DOM tree. They comprise their own tree. Therefore, the elements in the external image can't be matched by CSS selectors in the main document.

You can style the object element like you could most other elements, for example giving it a border. But you can't (this way, at least) access the elements in the external image. In your case, you try to style #ob's color. That would apply to the objects text color, not to any color inside the referenced svg image. On browsers not supporting svg, the "Your browser does not support SVG" notice would probably rendered in blue.

The case with your CSS selector for svg is similar: CSS selectors in the main document match only to elements in the main document, and there's no svg to be found, just an object.

There are some ways to apply CSS styling to svg elements. The idea generally is to bring the CSS and the svg elements to the same DOM tree, either by getting the svg elements from the external file to the main document or the CSS from the main document to the external file:

1. Embed your svg element and its child elements directly into the main document instead of referencing an external file. In this case, the svg element and its children will be part of the man document's DOM tree, so they're accessible to the main document's CSS.
2. Embed an svg element into your main document and use xlink's use to reference an external svg image (rather, a part of it). For the general idea, see this answer or this answer.
3. Load the elements from the external image to the main documents tree via AJAX/XHR. For the general idea, again see this answer.
4. You can grab a hold of the external images' tree with JavaScript and edit their styles from there. The keyword for that would be contentDocument, see this answer.
5. If you can't get the elements from your external svg image to your main document's DOM tree, so the main documents CSS selectors can match to it, you can try the other way around: Add your CSS to your svg file. Similar to the ways you can include CSS into a html document, you can use inline style attributes, use a style element like in html's head or reference an external CSS file with <?xml-stylesheet ... ?>. For more information, see for example this tutorial.