Change a color sitewide

Or do you belong to the buttons?

you can insert your wanted color to : General Styling – Main Content – Primary Color

but that will only work if the buttons are on default setting. If they are inserted with custom settings – it will have no effect.

ok – you can try first the last tip.
Then i will have a look if we can address it by attribute selector.

please insert this to your child-theme functions.php:
(maybe a mod knows a shorter way)

function replace_one_specific_color(){
?>
<script>
window.addEventListener("DOMContentLoaded", function () { 
(function($) {     

	function colorReplace(findHexColor, replaceWith) {
	  // Convert rgb color strings to hex
	  // REF: https://stackoverflow.com/a/3627747/1938889
	  function rgb2hex(rgb) {
	    if (/^#[0-9A-F]{6}$/i.test(rgb)) return rgb;
	    rgb = rgb.match(/^rgb\((\d+),\s*(\d+),\s*(\d+)\)$/);
	    function hex(x) {
	      return ("0" + parseInt(x).toString(16)).slice(-2);
	    }
	    return "#" + hex(rgb[1]) + hex(rgb[2]) + hex(rgb[3]);
	  }

	  // Select and run a map function on every tag
	  $('.flex_column, .avia-button').map(function(i, el) {
	    // Get the computed styles of each tag
	    var styles = window.getComputedStyle(el);

	    // Go through each computed style and search for "color"
	    Object.keys(styles).reduce(function(acc, k) {
	      var name = styles[k];
	      var value = styles.getPropertyValue(name);
	      if (value !== null && name.indexOf("color") >= 0) {
	        // Convert the rgb color to hex and compare with the target color
	        if (value.indexOf("rgb(") >= 0 && rgb2hex(value) === findHexColor) {
	          // Replace the color on this found color attribute
	          $(el).css(name, replaceWith);
	        }
	      }
	    });
	  });
	}
	// Call like this for each color attribute you want to replace
	colorReplace("#ea675b", "#0000DD");

})(jQuery);
});
</script>
<?php
}
add_action('wp_footer', 'replace_one_specific_color');