SSRS - Alternate Change Background Color of Matrix Row

Step 1: Select entire Row to apply background color

Step 2: go to Background Color from Property Explorer.

Step 3: Click on Drop Down Box and go to Expression.

Step 4: Add the following Code. 

=IIF(RunningValue(<Field_Value>,COUNTDISTINCT,NOTHING) MOD 2 = 0
,"Red",
"White")

Here <Field_Value> is that field which have alternate changed value.

Result: