When using Qiskit's plot_bloch_vector function, how can I set colors for vectors?

Question

I am able to visualize vectors on a bloch sphere using Qiskit as follows:

from qiskit.quantum_info import Statevector
from qiskit.visualization import plot_bloch_vector
%matplotlib inline

sv = []
sv.append([0,1,0])
sv.append([0,0,1])
sv.append([1,0,0])

fig = plot_bloch_vector(sv)
fig

The code above yields the following result (which looks good):

Now I would like to adjust the colors of each vector. The API of Qiskit seems not to provide any color parameter for plot_bloch_vector. Maybe we can manipulate the fig object directly or find another way to adjust vector colors?

Answer 1

A simple way to do that is by using Bloch class^[1] directly which accepts a list of vector colors to cycle through:

from qiskit.visualization.bloch import Bloch

_bloch = Bloch()
_bloch.vector_color = ['red', 'green', 'blue']

sv = []
sv.append([1,0,0])
sv.append([0,1,0])
sv.append([0,0,1])

_bloch.add_vectors(sv)
_bloch.render()
_bloch.fig

The result: