I think the general rule of thumb is you can pitch from light to dark directly on the cake.
That being said I washed a cake off an oatmeal coffee stout and repitched onto an ESB not too long ago. Another couple of weeks and I'll tell you how it turned out. It didn't seem to affect the color much as I washed the cake, but it may impart some of the stout flavors.
I wouldn't do that. First, I assume that the IPA was a higher OG than the cream ale. So, you'd be overpitching by quite a bit. Also, I'd assume that the IPA was heavily hopped, and those flavors would carry over.
You could easily wash the yeast, though, and use the correct amount without any worries at all.
Generally, you'd want to do it in the other order - cream ale followed by the IPA as you will get some hop transfer. If the IPA was not over the top in hop content/bitterness and you don't mind a bit extra hoppiness in the cream ale, go for it - you may love the results. Otherwise, best to wash before using.
Grvities and hoppiness was what I was worried about. As far as using the correct amount, after washing yeast, how does one determine an amount of yeast sitting in a jar? Thanks for the input folks!
I pitched an Irish Red on a Black PA cake from a recipe I created and being the first time it scared the S out of me. I got fermentation, a fairly solid one, we'll see what happens...
Grvities and hoppiness was what I was worried about. As far as using the correct amount, after washing yeast, how does one determine an amount of yeast sitting in a jar? Thanks for the input folks!