Bubble gum pink or pastel mint green were popular solid colors of that era. I Googled "butterly quilt depression" and clicked on "images" to get some photos of actual butterfly quilts of that era. Here's a link to what I got:
http://www.google.com/search?hl=en&sugexp=gsis,i18n%3Dtrue&cp=26&gs_id=r&xhr=t&q=butterfly+quilt+depression&qe=YnV0dGVyZmx5IHF1aWx0IGRlcHJlc3Npb24&qesig=f2PDfAcbLREsDYghm-QQOw&pkc=AFgZ2tkiRH3CSjwa4Onq22kEc1E_oqxlAXC4Ppnt416Kyb 3pss0O_32F6_iwpEOQjdOmeKP6LGG2wzwKmW3GD5p7-9axg-hh-A&qscrl=1&nord=1&rlz=1T4GZAG_enUS434US434&gs_sm=&gs_upl=&bav=on.2,or.r_gc.r_pw.&ion=1&biw=1466&bih=707&wrapid=tljp1316366071147020&um=1&ie=UTF-8&tbm=isch&source=og&sa=N&tab=wi
Personally, I'd look for an aqua because I like blue better than pink or green. A pastel purple might be nice if you could find the right shade.