What is controlling the top section of the site?

[DavidJk]

A friend asked me to fix up his Weebly site. I have built a lot of sites with WP. But I have very little experience with Weebly and it feels like learning a new language. The top bar currently on the site is very big and I want to decrease the height and change the color. But I can't figure out what's controlling it and how to access what's controlling it. 

Every page has the light green top bar so I am guessing that an app is controlling it. But I can't figure out which app or how to control the settings. Here are the apps installed on the site:

Accordion
Call-Out Box
Carouselstar
Ecwid Online Store
The Pop Up

Here is the URL to the site I am editing:  https://www.algagen.com/

Below is a screenshot of what I want to edit and added a red box for emphasis.

[Adam7]

From the list of apps I'd guess it's the The Pop Up App, although it could also be something added via a custom theme. I would check the settings for that app, and I would also go to Theme > Edit HTML / CSS and check the various page templates to see if it was added there.