fix/button/bg colors and contrast

packages/rocketchat-theme/assets/stylesheets/utils/_colors.import.less

@@ -265,7 +265,7 @@ blockquote:before {
 			background-color: @content-background-color;
 		}
 		.message-buttons {
-			.buttonColors(@primary-font-color, @transparent-dark);
+			.buttonColors(lighten(@primary-font-color, 25%), @secondary-background-color);
 		}
 	}
 	.new-message {

packages/rocketchat-theme/assets/stylesheets/utils/_mixins.import.less

@@ -92,7 +92,7 @@
 	color: @color;
 	background-color: @bg;
 	&:hover {
-		color: lighten(@color, 10%);
-		background-color: darken(@bg, 5%);
+		color: mix(@color, contrast(@bg), 60%);
+		background-color: fadein(mix(@bg, contrast(@color), 60%), 25%);
 	}
 }

packages/rocketchat-theme/server/variables.coffee

@@ -24,7 +24,7 @@ majorColors=
   'primary-action-color': '#13679A' # was action-buttons-color
   'secondary-background-color': '#F4F4F4'
   'secondary-font-color': '#A0A0A0'
-  'secondary-action-color': '#E5E5E5'
+  'secondary-action-color': '#DDDDDD'
   'component-color': '#EAEAEA'
   'success-color': '#1DCE73'
   'pending-color': '#FCB316'