---
id: 5d822fd413a79914d39e98d7
title: Part 15
challengeType: 0
---
## Description
To use a variable, just put the variable name in parenthesis with `var` in front of them like this: `var(--variable-name)`. Add your variable as the value of the `background-color` property of the `bb1a` class. Whatever value you gave the variable will be applied to whatever property you use it on. In this case, your variable has the value of `#999`. So `#999` will be used as the value for the `background-color` property.
## Instructions
## Tests
```yml
tests:
- text: test-text
testString: const bb1aStyle = code.match(/\.bb1a\s*{[\s\S]+?[^}]}/g)[0]; assert(/background-color\s*:\s*var\(\s*--building-color1\s*\)\s*(;|\s*})/g.test(bb1aStyle));
```
## Challenge Seed
```html
freeCodeCamp Skyline Project
```