specifying list of colors does not work for me

[mathause]

MCVE Code Sample

import xarray as xr
import numpy as np

airtemps = xr.tutorial.load_dataset('air_temperature')

air = airtemps.air.isel(time=0)


levels = np.arange(225, 301, 25)

colors = ['#ffffb2', '#fecc5c', '#fd8d3c', '#e31a1c']

# this does not work for me
air.plot.pcolormesh(levels=levels, colors=colors)

Expected Output

Should create a plot with the specified colors. According to the the docstring this should work. Or maybe I am doing something wrong here?

Problem Description

Instead I get the following error:

/usr/local/Miniconda3-envs/envs/2019/envs/iacpy3_2019/lib/python3.7/site-packages/xarray/plot/utils.py in _process_cmap_cbar_kwargs(func, kwargs, data)
    683     # colors is only valid when levels is supplied or the plot is of type
    684     # contour or contourf
--> 685     if colors and (('contour' not in func.__name__) and (not levels)):
    686         raise ValueError("Can only specify colors with contour or levels")
    687 

ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all()

Instead I use the following, which works:

air.plot.pcolormesh(levels=levels, cmap=colors)

Output of xr.show_versions()

INSTALLED VERSIONS ------------------ commit: None python: 3.7.1 | packaged by conda-forge | (default, Feb 18 2019, 01:42:00) [GCC 7.3.0] python-bits: 64 OS: Linux OS-release: 4.12.14-lp151.28.13-default machine: x86_64 processor: x86_64 byteorder: little LC_ALL: None LANG: en_GB.UTF-8 LOCALE: en_US.UTF-8 libhdf5: 1.10.4 libnetcdf: 4.6.2

xarray: 0.12.1
pandas: 0.24.2
numpy: 1.16.2
scipy: 1.2.1
netCDF4: 1.5.0.1
pydap: installed
h5netcdf: 0.7.1
h5py: 2.9.0
Nio: None
zarr: 2.3.1
cftime: 1.0.3.4
nc_time_axis: 1.2.0
PseudonetCDF: None
rasterio: 1.0.22
cfgrib: 0.9.7
iris: 2.2.0
bottleneck: 1.2.1
dask: 1.1.5
distributed: 1.26.1
matplotlib: 3.0.3
cartopy: 0.17.0
seaborn: 0.9.0
setuptools: 41.0.0
pip: 19.0.3
conda: None
pytest: 4.4.0
IPython: 7.4.0
sphinx: 2.0.1

[mathause]

I just found out - the error actually comes from using a numpy array to the define the levels (and (not levels)) and not from using colors. So it is in a way a user error. However, I suppose it would be good to support numpy arrays to pass levels?