Apparent Magnitude

The change in apparent magnitude of a star, according to its spectral class and doppler factor D.

Note that an increase in brightness corresponds to a decrease in stellar magnitude.

Here, each spectral class is mapped internally to a representative absolute temperature in degress Kelvin.

In general:

there's always a value of D for which the brightness has a peak.
the cooler, redder stars have a greater increase in brightness for doppler factor D>1.
the hottest, bluest stars get dimmer for almost all values of D.