fig1 = figure()
annotate('$e^{-x/5}$' + '$e^{-x/1}$', xy=(x[10], exp2[10] + exp1[10]),
    xytext=(40, 20), textcoords='offset points', ha='center', va='bottom',
    color='white', bbox=dict(boxstyle='round,pad=0.2', fc='yellow', alpha=
    0.3), arrowprops=dict(arrowstyle='->', connectionstyle='arc3,rad=-0.5',
    color='r'))
matplotlib two different colors in the same annotate