Expression background colours only displaying for selected month
I have a chart that dynamically displays aggregates by company for the last 12 months based on the current selected month. It should also format the expression background colour based on the company name (company names and their corresponding colours are stored in a table). In the attached example with dummy data, the line chart appears fine, but the pivot table only formats the expression for the current selected month. What changes can I make so that the pivot table displays the colours for all 12 months?
Just a note that the attached example only has three company names in the sample data, but the actual data has over 20, and it is possible that more company names could be added in future. If possible I would like to avoid hard coding these, and only add colours for a new company name in the colour table, which will then be picked up by the chart.