weird problem with ms graphs

[rocklee]

I have a graphs that simply looks up a table and counts the number of students present and absent with the following code :

TRANSFORM Count([Activity Attendance].[Activity ID]) AS [CountOfActivity ID]
SELECT [Activity Attendance].AttendanceDate
FROM [Activity Attendance] INNER JOIN Student ON [Activity Attendance].UPN = Student.UPN
GROUP BY [Activity Attendance].AttendanceDate
PIVOT IIf([Activity Attendance].[InClass],"Present","Absent");

The table has a toggle field (yes/no) that I use to mark attendance.

This works very well and I use 2 colours, yellow for students present and purple for absentees.

The problem is when all students are present, it will use purple instead of yellow.

 

[rocklee]

Any idea guys?