Question

This cross will yield four phenotypes in the 1:1:1:1 ratio:

Answer 1

RrYy x rryy will yield the phenotypic ratio you want, I think

Answer 2

The answer would be:

RrYy x rryy

Here's more about your question:

The Punnet square for this cross is attached below.

As you can see the results will be:

RrYy = 4/16 = 1/4

rrYy = 4/16 =  1/4

Rryy = 4/16 = 1/4

rryy = 4/16 =  1/4

All four phenotypes have a 1/4 chance of occurring. So the ration between them would be 1:1:1:1