To set the linear transparent header style, navigate to your website admin, browse to Appearance > Customize > Header > General, from the header style dropdown, select Linear Transparent.
Additional Header Settings for the Linear Transparent Style
Setting the Background Color
While it’s transparent, but you can set the background color for this style if you prefer.
To choose the background of your choice, just click over the “Select Color” button available under the “Background Color” label in General panel.