feat(theme): Update baseline theme colors (#1884)

The baseline color values are duplicated in demos/common.scss because we still want to demonstrate how and where to set your own custom colors.

The theme demo page will soon let you preview multiple themes, at which point we might want to remove the duplicate color values from common.scss.

demos/common.scss

@@ -21,9 +21,8 @@
 @import "../packages/mdc-theme/color-palette";
 
 // Base style
-$mdc-theme-primary: $material-color-grey-900 !default;
-$mdc-theme-primary: $material-color-blue-500 !default;
-$mdc-theme-secondary: $material-color-light-green-a700 !default;
+$mdc-theme-primary: #6200ee !default; // baseline purple, 500 tone
+$mdc-theme-secondary: #018786 !default; // baseline teal, 600 tone
 
 // Import button and ripple mixins to apply overrides for dark theme
 // TODO(kfranqueiro): Pending further design discussion around how to manage dark theme

packages/mdc-theme/_variables.scss

@@ -22,13 +22,13 @@
 // If you're a user customizing your color scheme in SASS, these are probably the only variables you need to change.
 //
 
-$mdc-theme-primary: #3f51b5 !default; // Indigo 500
+$mdc-theme-primary: #6200ee !default; // baseline purple, 500 tone
 $mdc-theme-primary-light: mdc-theme-light-variant($mdc-theme-primary) !default;
 $mdc-theme-primary-dark: mdc-theme-dark-variant($mdc-theme-primary) !default;
 
 // The $mdc-theme-accent variable is DEPRECATED - it exists purely for backward compatibility.
 // The $mdc-theme-secondary* variables should be used for all new projects.
-$mdc-theme-accent: #ff4081 !default; // Pink A200
+$mdc-theme-accent: #018786 !default; // baseline teal, 600 tone
 $mdc-theme-secondary: $mdc-theme-accent !default;
 $mdc-theme-secondary-light: mdc-theme-light-variant($mdc-theme-secondary) !default;
 $mdc-theme-secondary-dark: mdc-theme-dark-variant($mdc-theme-secondary) !default;