Expression Issue for X-axis Label SSRS

HI Experts, 

I had small issue. 

I have written one expression to display date coloures based on weekend or Public holiday.

=IIF(Fields!TypeOfDay.Value="Weekend" OR Fields!IsaPublicHoliday.Value="True","Red","Black")

The X-axis coloumn is [YYYYMMDD]  

I have tried same thing in the table It was working fine though it is not working in the chart level.

I dont understand where I was doing mistake