You can customize story button style.

Background Color Type: Choose basic background or gradient background.
Background Color: Choose button background color.
Text Color: Choose button text color.
Font Size: Choose button font size.
Padding: Choose button vertical and horizontal padding.
Border Radius: Choose button border rounded size.
Also, you can set this options for each story.
For doing this, just go Story Box options, and set Enable Custom Style to Custom value.
