TodayTix with someone's discount code, if you never used the app before (eh, what the hell, use mine VGWAW) is probably your best bet. That would get you a $65 ticket ($75-$10). That may be as cheap as you can get in...
But SRO seems unlikely, and even TKTS doesn't always offer all price levels at 50% off, since they usually try to unload the pricier tickets.
The only other option is if you are a TDF member, since they sometimes have Color Purple tickets (although not yet for Saturday), but if you aren't, and if you qualified, by the time you paid the annual membership fee, you would go over the $65 above.