See #554 (comment)

This appears to be a theming edge case

Essentially, a strip plot is a box plot with the box hidden and all points showing.
The edge case arises because of how that box is hidden

import deephaven.plot.express as dx

stocks = dx.data.stocks()

fig_strip = dx.strip(
    stocks, 
    x="Price",
    by="Sym"
)

This is the same case as Alex originally posted, it's just empty
Note that these traces have 'line': {'color': 'rgba(255,255,255,0)'}
Setting that alpha to 0 is what makes the box transparent of course
Now see this example

def testb(f):
    f.update_traces(line={'color': 'blue'}, boxpoints="all")
    
fig_strip_blue = dx.strip(
    stocks, 
    x="Price",
    by="Sym",
    unsafe_update_figure=testb
)

As you can see, the points themselves are inheriting the color from line

This can of course be overriden, I'll just do it through unsafe_update_figure

def testrb(f):
    f.update_traces(line={'color': 'blue'}, boxpoints="all", marker={'color':'red'})
    
fig_strip_red_blue = dx.strip(
    stocks, 
    x="Price",
    by="Sym",
    unsafe_update_figure=testrb
)

But, the problem is, we strip the marker color (as we should) but since we use the colorway for the theme, the marker inherits the transparent line color
I can remove the line color and this is themed "properly", but then the line is there when we don't want it.

def testl(f):
    f.update_traces(line=None, boxpoints="all")
    
fig_strip_themed = dx.strip(
    stocks, 
    x="Price",
    by="Sym",
    unsafe_update_figure=testl
)

@bmingles @mattrunyon what do you think would be the best solution for this?

@jnumainville Why does line=None still show the lines?

Because the way they are hidden is through setting the line color to be completely transparent in the trace
'line': {'color': 'rgba(255,255,255,0)'}
Setting line=None doesn't get rid of the lines, just the color

@jnumainville How about setting line width to 0.

f.update_traces(line={'color':None,'width': 0}, boxpoints="all")

That almost works, but the legend doesn't show up correctly. I'm guessing plotly doesn't handle a width of 0 in the legend.
This happens in plotly and px too. Might be worth opening a ticket.

import plotly.express as px

df = px.data.tips()

fig = px.strip(df, x="total_bill", y="day", color="time")
new_fig = fig.update_traces(line={"color": None, "width": 0})
new_fig.show()

I opened plotly/plotly.js#7159

PR opened against plotly for this: plotly/plotly.js#7162