Conditional Formatting on a matrix grouped by Column

Use the following logic below, but keep it mind that you need a proper Date dimension table and make "mark as date table" checked.

1) Base measure

Sales Total =
SUM ( FactSales[SalesAmount] )

2) Previous Year Sales

If you have a proper Date table related to your fact:

Sales PY =
CALCULATE(
    [Sales Total],
    DATEADD( DimDate[Date], -1, YEAR )
)

3) YoY change measure 

Sales YoY % =
VAR Prev = [Sales PY]
RETURN
IF( ISBLANK(Prev), BLANK(), DIVIDE([Sales Total] - Prev, Prev) )

4) Icon rule measure

Use +1 / -1 to simplify icon rules:

Sales Trend Flag =
VAR d = [Sales YoY Change]
RETURN
IF(
    ISBLANK(d),
    BLANK(),
    IF( d >= 0, 1, -1 )
)

5) Apply conditional formatting (icons)

In the matrix:

• Values → Sales Total

• Conditional formatting → Icons

• Format by: Rules

• Based on field: Sales Trend Flag

• Rules:

  • If value >= 1 → green up arrow

  • If value <= -1 → red down arrow