TranslucentTB is an Open Source app that allows you to tweak the appearance of the taskbar.

With TranslucentTB, you can customize the effect, color, and combine states (maximized window, Start Menu open, Cortana open, and Timeline open), each with a customizable taskbar appearance you can attain a dynamically changing and visually pleasing taskbar. It also offers a dynamic option, which permits TranslucentTB to hide it only when there is no maximized window.

When enabled, it works to only show your pinned Win32 and UWP apps against your wallpaper, giving you a unique custom look to your desktop above and beyond what is found by default. It is designed to be as simple to configure and use as possible.

TranslucentTB Features:

Advanced color picker supporting alpha and live preview to change the taskbar's color.

Taskbar states (choose one - color can be customized on every state except Normal):
-Blur: Will make the taskbar slightly blurred.
-Clear: Transparent taskbar.
-Normal: Regular Windows style. (as if TranslucentTB was not running)
-Opaque: No transparency.
-Fluent: Windows 10 April 2018 update and up only. Will give the taskbar an appearance similar to Microsoft's Fluent Design guidelines.

Dynamic modes (these can be used together, and each of them provides a taskbar state and color you can customize):
-Dynamic Windows: Will change the taskbar to a different appearance if a window is currently maximized.
-Dynamic Start Menu: Will change the taskbar appearance when the start menu is opened.
-Dynamic Cortana: Will change the taskbar appearance when Cortana (or the search menu if Cortana is disabled) is open.
-Dynamic Timeline/Task View: Will change the taskbar appearance when the Timeline (or Task View on older builds) is open.

Ability to show or hide the Aero Peek button. Can be customized at will or dynamic.

Similar:

Enable or Disable Taskbar Transparency in Windows 10

How to Customize the Windows 10 Taskbar

How to Show or Hide the Search Box or Search Icon in Windows 10