Scipy spectrogram of .wav file looks violet

Question

import os
import scipy.io
import scipy.io.wavfile
import numpy as np
import matplotlib.pyplot as plt
from scipy import signal
from scipy.signal import spectrogram, get_window

dataset_path = os.path.join(os.environ['HOME'], 'shared', 'data', 'assignment_1')
wavedata = os.path.join(dataset_path, 'example.wav')
   
fs, audio_buffer = scipy.io.wavfile.read(wavedata)

a = np.array(audio_buffer)


window = get_window('hann', frame_size)  # we will us a Hann window for the DFTs
    
freqs, times, spec = scipy.signal.spectrogram(audio_buffer, fs, window='hann')

plt.pcolormesh(times, freqs, spec)
np.log(spec)
plt.ylabel('Frequency [Hz]')
plt.xlabel('Time [sec]')
plt.show()

I tried to make a spectrogram. The problem is that it is almost completely violet. How can I fix this?