fix(learn): add example in building a set of colored markers (#46312)

curriculum/challenges/english/14-responsive-web-design-22/learn-css-colors-by-building-a-set-of-colored-markers/61764c602bee6974e7790f35.md

@@ -13,6 +13,12 @@ These days, there are two main color models: the <dfn>additive</dfn> RGB (red, g
 
 First, add the `class` `one` to the first marker `div` element.
 
+```html
+<div class="exampleClass1 exampleClass2">
+  ...content
+</div>
+```
+
 # --hints--
 
 You should add the class `one` to the first marker `div` element.