Now if you want to stress out the key and value for example you only want to pull posts that has a custom field key color and the value as blue, then your query code will look liks this:
How to Add Custom Fields to Your WordPress Posts
For example, let’s say you wanted to indicate which of the posts on your blog are sponsored to ensure you’re being transparent with your audience. You could add a short disclosure statement to each relevant post individually. Alternatively, you could save some time by using a custom field that displays a relevant message. Then, you could add code to your theme file that would make your disclosure statement show up on the correct posts.