If you want to target paths of an svg, and use standard CSS rules, it has to be an .svg vector file.
You can create them in a variety of programs. In Adobe Illustrator, you 'save-as' > 'svg' > note the bottom of that pane - see the svg code > copy it > past it somewhere smart.
The png is a bitmap and is just a square you can resize and turn and stuff.
HTML
<div class="image-w bitmap-logo">
<img src="http://placehold.it/400x200" alt="" />
</div>
<div class="image-w svg-logo">
<?php require('big-svg-thing.php')?>
or...
{{partial 'big-svg-thing'}}
</div>
If you use PHP or handelbars or htmlbars etc... just to keep the svg code out of your way.
CSS ideas for you
With images that need to resize all the time... I put them in .image-w
to control them and to compress their pixels for retina screen.
Attached is a fiddle --- because the svg is super ugly/long code
Note that I added classes to the parts of the svg that I wanted to style
/* global / overall image styles */
.image-w img, .image-w svg {
display: block;
width: 100%;
height: auto;
}
svg path { /* good preset for svg / sets 'fill' to casdade like color */
fill: currentColor;
}
.bitmap-logo { /* things you might do with you bitmap */
max-width: 200px;
transform: rotate(10deg);
opacity: .2;
border: 2px solid red;
}
.svg-logo { /* svg */
max-width: 300px;
}
.svg-box { /* parts of the svg */
color: blue;
}
.svg-squigle {
color: red;
}