[plt-dev] Multi-color calculi in Redex

I would like to define the following grammar in Redex:

e := .... | let x = e in e | {e}_i 

E_0 := [] | let x=E_0 in e

E_i := let x = E_i in e | {E_0}_i | {E_i}_j

where i,j in N^*.

Do you have any ideas how I could code that in Redex?

Thank you.

.Christos