Вы можете просто зациклить:
import pandas as pd
df = pd.DataFrame({
'x' : [1,2,3],
'y0' : [1,3,2],
'y1' : [2,1,3],
})
colors = ['red', 'blue']
from bokeh.io import show
from bokeh.models import ColumnDataSource
from bokeh.plotting import figure
source = ColumnDataSource(df)
p = figure(plot_height=250)
i = 0
for name in df.columns:
if not name.startswith('y'): continue
p.line('x', name, color=colors[i], source=source)
i += 1
show(p)