Beatflyer includes a selection of beautiful color theme that can be quickly applied to templates:

If you have a paid subscription, you can also create your own themes. For instance if you need to follow certain brand guidelines.

You can create your custom color themes in your account settings:

When creating a color theme you have 3 colors that you can set. The preview on the top makes them quite clear. The one perhaps which is less obvious is the "accent" color. This is generally used by few words that need to stand out.