Signature fill block color change

I frequently use Adobe Sign to send contracts to my clients for their signatures. There are usually three signatories: me and two recipients. 

My issue is this: the first signature block appears with bright yellow fill. That's fine, as is the second, with pink fill. The problem is the third block, which is pale yellow. My contracts require the recipients to sign in quite a few places, and it is easy for me to mistake one yellow signature block for another as I'm setting up the form. I sometimes don't catch this until it's too late, and I have to start the field-generating process fro scratch.

So, is there a way to globally change the color of the fill in the signature blocks?

The Adobe Chat person said today (in poor English) that it is not possible.

Thanks!