Putting space between every two bars in seaborn's factorplot

I have a drawn a plot using seaborn and the following command:

ax = sns.factorplot(x="feat", y="acc", col="roi", hue="alpha", data=df_d_pt, kind="bar", dodge=True)

Results look like this:

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But I want to put space between every two bars, that is bars with dark blue and light blue would be very close to each other but some space between the dard blue bar and the light green one (and so on...)

How can I do that?

Thanks in advance