Great pic, interesting, bulb is somewhat similar, but different from the WiFi bulb I opened: Sylvania Smart+ RGBW which are available OTC here at $5 for two.
BP5778 8-pin IC is 2-channel linear constrant-current driver, from datasheet found which is mostly in chinese. Exactly how the LEDs are connected is not obvious, but I imagine R, G, and B are on separate series chains. Four each at 32v each makes sense.
For white flexibility, looks like 7 warm white, 7 cool white, and 7 yellow LEDS around perimeter. Likely they are driven by circuitry "below deck" through P1 pins. You would think interspersing/spreading these would create good mixing, but they are grouped together.
Not sure what is on P1 pins, could be low-voltage PWM to control R/G/B drivers, plus drive voltage (possibly hazardous) for white and yellow LEDS. Without figuring out pin assignments,
measuring would be of limited use, and could change depending on the light setting.
On that note insulating gloves are a good idea, plus some eye protection. Consequence of shorting with DMM probes could range from no effect (current limited) to damage, smoke/sparks (with some risk of fire), burn from hot metal, and electric shock. Even after bulb is powered off, a capacitor could hold high voltage for a short period.
As for diagnosing the blue LED issue, not sure how far you want to go. If it's a driver problem, finding replacement chip and removing/reinstalling could be challenging. It would likely involve a hot air gun, as chip has a bottom pad soldered to the PCB. As for checking individual LEDs without removing them, I have some ideas, let me know if you want further detail.
Dave