How to have joined line segments with different stroke colours in Adobe Illustrator?

Question

I have two line segments: one with a black stroke and one with a red stroke. Both have a stroke weight of 0.25pt.

I'd like to joint the two paths and treat them as a single path, but with the two different colours. However, when I join them with the Cmd/Ctrl + J shortcut, the two segments fuse together and the stroke colour is changed to black in both.

Now, is it possible to achieve such a desired effect? Any smart workaround?

Answer 1

In principle, any single stroke can only have a single colour attribute at any one time. As joining creates one stroke out of two, this is true for the end result.

However, a gradient is also a 'colour attribute', and it's possible to cheat using a gradient that has a very sharp turnover.

1. Select your joined stroke;
2. In the toolbox, click the stroke icon so it's selected rather than the fill;
3. Get your gradient palette, using Window > Gradient or Ctrl/Cmd+F9;
4. In the palette, click the gradient example square on the top left to apply this gradient to your stroke;
5. Click the second 'stroke' icon in the Gradient palette to apply the gradient over the length of the stroke;
6. Drag colour stops from your Swatches palette onto the gradient bar in the palette to add the desired colours as necessary—delete colour stops by dragging them downwards off the palette;
7. End up with a gradient with two colour stops;
8. Drag the two stops as close together as they will go; use the 'location' field to fine-tune if necessary;
9. Find the sweet spot where the effect replicates a sharp colour switch exactly in the location you want.