Change agency banner color to AA accessibility vaild colour (#258)

Several agencies, OPG, HMCTS and JO had header banner colours that did
not meet AA accessibility standards when white external link text was
overlayed ontop. This fixes that with AA compliant colours. All colours
have been approved by the agencies.

wp-content/themes/clarity/src/globals/css/_variables.styl

@@ -51,14 +51,14 @@ rupture.scale-names = 'xxs' 'xs' 's' 'm' 'l' 'xl' 'xxl';
 $defaultAgencyColour = #005ea5; // default Gov blue
 $socialLinks    = #005ea5;
 $cica_primary   = $defaultAgencyColour;
-$hmcts_primary  = #67b2e8;
+$hmcts_primary  = #1B75B6;
 $hmpps_primary  = $defaultAgencyColour; // previously called 'noms'.
 $jac_primary    = $defaultAgencyColour;
-$jo_primary     = #008998;
+$jo_primary     = #00818F;
 $lc_primary     = #006666;
 $hq_primary     = $defaultAgencyColour;
 $nps_primary    = $defaultAgencyColour;
-$opg_primary    = #76b700;
+$opg_primary    = #00838F;
 $pb_primary     = #ab0755;
 $ppo_primary    = $defaultAgencyColour;
 $laa_primary    = #156c60;