SOLUTION (part 1) - I was able to flash new code by entering Safe Mode:
To put your device in Safe Mode:
• Hold down BOTH buttons
• Release only the RESET button, while holding down the SETUP button.
• Wait for the LED to start blinking magenta
• Release the SETUP button
This put the Photon in a state that was easily flashed.
ISSUE (color flashes) - Here are the two flashes that I'm getting when I run the code above:
&
PROBLEM (I2C issue) - Code that eliminates the Wire.beginTransmission(); and Wire.endTransmission(); statements just sits there, prints to Serial.print(), and pulses like it should.
So I'll start trying to dissect what the problem is, and will update. I've noticed I2C issues previously.