How to update C3.js graph line width and tick color?

For case of increasing scatterplot circle radius, radius of circles on line charts. Please use like this:

c3.generate({
...
  point: {
    r: 10,
  },
...
})

If you use a DOM inspector you can see what classes the different objects have and then it's just a case of assigning some CSS to them e.g.

.c3-line {
    stroke-width: 2px;
}

.c3-circle {
    fill: red !important;
}

As per documentation you can control line width individually by following

[chart-id] .c3-line-[chart-data-name] {
  stroke-width: 5px;
}

if it does not work try to use !important

ex:

#chart .c3-line-data2 {
  stroke-width: 5px;
}