Hi @yogi_dhiman, same approach as in the scatter plot 
fig.update_traces({'marker':{'size': your_desired_size}})
Full example:
import plotly.express as px
df = px.data.tips()
fig = px.strip(df, x='total_bill', y='day')
fig.update_traces({'marker':{'size': 50, 'color': 'pink'}})
creates:
