dataframe_highlight.py

df2 = df.copy()
df2['year'] = df2.reset_index().DATE.dt.year
df2['month'] = df2.reset_index().DATE.dt.month
df2['pct_chg'] = df2['HOUSTNSA'].pct_change()

avg_chg_month = df2.groupby('month')['pct_chg'].mean().reset_index()
avg_chg_month['pct_chg_std'] = df2.groupby('month')['pct_chg'].std().values
avg_chg_month['pct_chg_2016'] = df2.loc[df2['year'] == 2016,'pct_chg'].values
avg_chg_month['pct_chg_2020'] = df2.loc[df2['year'] == 2020,'pct_chg'].values
avg_chg_month['pct_chg_2021'] = df2.loc[df2['year'] == 2021,'pct_chg'].values

def highlight_rows(row):    

    lightgreen = 'background-color: lightgreen;'
    highlight = 'background-color: lightcoral;'
    default = ''
    
    if row['month'] == 3:
        return [default,lightgreen,lightgreen,default,default,highlight]
    elif row['month'] == 4:
        return [default,lightgreen,lightgreen,default,highlight,default]
    elif row['month'] == 10:
        return [default,lightgreen,lightgreen,highlight,default,default]
    else:
        return [default,lightgreen,lightgreen,default,default,default]

avg_chg_month.style.apply(
    highlight_rows, 
    axis=1
).format(
    {var:'{:.1%}'.format for var in avg_chg_month.iloc[:,1:]}
)