I'm trying to get rid of this icon for a site I'm using.
Does anyone know how to get rid of it or at least change color so it is no longer visible.
That icon only shows in the Course Overview block in Moodle 3.5 and earlier, and only if activity completion is NOT enabled in a course (see Moodle docs).
You can hide it using custom CSS...
.progress-chart-container {display: none;}
but it will also hide the completion percentage display for courses where activity completion IS enabled.
It depends on your theme where you add your custom CSS, but in Boost, go to Site Administration > Appearance > Themes > Boost > Advanced settings and add it in the 'Raw SCSS' box.
The Course Overview block has changed from Moodle 3,6 onwards - see https://docs.moodle.org/36/en/Course_overview