Colored bloom-like artifacts can happen for more than one reason.

First, image sensors record separate red, green, and blue channel data. A very bright light source usually does not drive all three channels to saturation in exactly the same way. If a blue light is much stronger in the blue channel than in red or green, the saturated spill or clipped area can still look blue rather than white.

Second, not every bright colored glow or streak is true sensor blooming. Some artifacts come from sensor/readout behavior, where an overloaded pixel affects nearby pixels or even an entire row/column. Others are optical effects, such as diffraction or flare in the lens/aperture, and those can also preserve or emphasize the source color.

So the short answer is: your assumption is too narrow. Some blooming/readout artifacts can remain colored because the RGB channels saturate differently, and some colored streaks are caused by optical effects rather than charge overflow alone.