Rachel Allan 7170 dresses are available in the following colors: Periwinkle, Purple. $438 is the Formal Approach best price guarantee for style 7170 by Rachel Allan. Formal Approach is an authorized Rachel Allan prom dress store. We only offer authentic designer prom dresses. Rachel Allan 7170 comes in the following sizes: 0, 2, 4, 6, 8, 10, 12.