I have a dataset like this, but there are more rows

There I have employees` names and their qualifications in my project, start date and end date of their vacations and vacations` id.
Then i did an area bar chart (gantt chart) based on this dataset. Lines are grouped by vacation_id, start of line is vacation start date and end of line is vacation end date. The vertical axis shows the names of the workers, and the horizontal axis shows the dates of current month.
All lines are blue now. But I need to switch the lines color to red if vacations overlap by dates for those employees who have the same qualifications in my project.
Is it possible to do this?
