You can custom the appearance of the regression fit in a scatterplot built with seaborn.
In this example color, transparency and width are controlled through the line_kws={} option with the following elements:
color: color of the linealpha: opacity value of the linelw: line width
# library & dataset
import seaborn as sns
import matplotlib.pyplot as plt
df = sns.load_dataset('iris')
# plot
sns.regplot(x=df["sepal_length"], y=df["sepal_width"], line_kws={"color":"r","alpha":0.7,"lw":5})
plt.show()
