update color btns accessibility (#329)

Author: Arhell

_includes/head.html

@@ -65,7 +65,8 @@
           href="https://assets.phalcon.io/phalcon/css/core.min.css">
     <link rel="stylesheet"
           href="https://assets.phalcon.io/phalcon/css/custom.min.css">
-
+    <link rel="stylesheet"
+          href="../assets/fix.css">
     <title>
         {{ site.data.languages[page.language][page.title] }} - {{ site.app.title }}
     </title>

assets/fix.css

@@ -0,0 +1,3 @@
+html.dark .green-button {
+    background-color: #273646;
+}