Change the theme of your workspace
Microsoft Expression Blend comes with two themes for the workspace: Expression dark and Expression light. Changing your workspace theme does not affect the appearance of your project.
The themes of the Expression Blend workspace: dark (left) and light (right)
To change your workspace theme
On the Tools menu, click Options.
In the Options dialog box, select Workspace (on the left).
Next to Theme, select either Expression dark or Expression light. The theme changes immediately so that you can preview it.
Click OK.