Fix: unify blue background shades in all sections (#111)

Author: Kish-b

src/_includes/footer.njk

@@ -1,5 +1,5 @@
 {% from "components/button.njk" import button %}
-<footer class="bg-blue-600 flex text-white mb-0 bottom-0 w-full relative">
+<footer class="bg-pycon-blue flex text-white mb-0 bottom-0 w-full relative">
     <div class="relative mx-[6%] md:mx-[12%] mt-24 pb-8 md:pt-20 md:pb-12 w-full md:w-auto">
         <div class="xl:scale-125 text-center md:text-left">
             {{ button(text="Become a Volunteer", url="https://docs.google.com/forms/d/e/1FAIpQLSdX2LEom11BbWDiLUiQp1rmeNX9l7J8bfszGidsRDoExy0D5A/viewform", lime_bg=true, env = env) }}

src/_includes/landing/communities.njk

@@ -1,6 +1,6 @@
 {% from "components/button.njk" import button %}
 
-<section class="bg-blue-600 text-white relative px-4 sm:px-20 md:px-40 pt-10" id="communities">
+<section class="bg-pycon-blue text-white relative px-4 sm:px-20 md:px-40 pt-10" id="communities">
     <div class="mx-auto py-16">
         <div class="grid grid-cols-1 md:grid-cols-2 gap-4 sm:gap-10">
             <div>

src/_includes/landing/sponsors.njk

@@ -1,6 +1,6 @@
 {% from "components/button.njk" import button %}
 
-<section class="bg-blue-600 text-white relative px-4 sm:px-20 md:px-40 pt-10" id="sponsors">
+<section class="bg-pycon-blue text-white relative px-4 sm:px-20 md:px-40 pt-10" id="sponsors">
     <div class="mx-auto py-16">
         <!-- Desktop image visible -->
         <div class="grid grid-cols-1 md:grid-cols-2 gap-4 sm:gap-10">