Variable input to switch between Single Colour and Colour by Dimension

[SBFRFL]

I have a stacked Graph using two dimensions. One is 'completed date year week' and then Stacked is 'Application Date'. I would like to colour by dimension using 'Application date'

The graph looks very busy with all the colours 'Application date' adds in there, but there is value in having this info when you drill further down in to day of week etc so I want to keep it in. 

Im trying to give the to the user the option to see just 'Completed date year week' or to add in 'Application date' via a variable input. 

However if just viewing Completed date year week I dont want the graph coloured by dimension. I want a single colour. 

When selecting to view stacked with application date I want it to colour by dimension 'application date'.

Is this possible? 

Ive tried this in colour by dimension but it doesnt work. 

=if(vDimension1=1,blue([Completed Date (ApplicationAction).autoCalendarExtn.YearWeek]), if(vDimension1=2,[Application Date (Application).autoCalendar.Date]))