added 01-responsive-web-design/basic-css/ (#22531)

I have added use rgb-to-mix-color

curriculum/challenges/english/01-responsive-web-design/basic-css/use-rgb-to-mix-colors.english.md

@@ -82,6 +82,27 @@ tests:
 <section id='solution'>
 
 ```js
-// solution required
+<style>
+  .red-text {
+    color: rgb(255, 0, 0);
+  }
+  .orchid-text {
+    color: rgb(218, 112, 214);
+  }
+  .sienna-text {
+    color: rgb(160, 82, 45);
+  }
+  .blue-text {
+    color:rgb(0, 0, 255);
+  }
+</style>
+
+<h1 class="red-text">I am red!</h1>
+
+<h1 class="orchid-text">I am orchid!</h1>
+
+<h1 class="sienna-text">I am sienna!</h1>
+
+<h1 class="blue-text">I am blue!</h1>
 ```
 </section>