Not quite - it's not uint32_t that's doing the magic here. That's just a variable type (32 bit unsigned integer).
The Color() function is the important bit. It takes the three separate RGB values, and combines them into a single 32 bit number that you can store for later use.
It's explained here, about half-way down. Arduino Library Use | Adafruit NeoPixel Überguide | Adafruit Learning System