Can you identify which specific systems are showing the problem or is it just random?
I've tested in Chrome on PC, Mac and ios and all our showing the correct image and color so its very difficult to debug unless we can find a machine it happens on.
There are a couple of things to check and you do have a js error in the console which may upset something along the way.
Fix that error (probably will require a trip to the js forum).
I also note that your html for the button is invalid.
<a class="telephoneCTA" href="tel:7817913150"><button>Call Now<br>781-791-3150</button></a>
A button cannot be a child of an 'a' element (or vice versa). I wouldn't be surprised if some browsers get confused by that. Either it's a link or its not. A button is an action and has its own methods. They are not compatible with each other although they can at times appear to do the same things. Use one or the other but not both at the same time
There may also be an issue where some browsers automatically style telephone numbers but I don't think that's an issue here.