Make chart categories distinguishable beyond color

Use an illustrative chart comparing three workshop groups: North, East and West. Give North a solid line with circular markers, East a dashed line with square markers and West a dotted line with triangular markers. Add each name beside its final point. Colors may reinforce the grouping, but the chart must remain interpretable through the other cues.

Write a series specification with name, color, marker, line pattern, label position and collision rule. This prevents a later scene from reusing a triangle for a different category simply because the palette changed. W3C’s Use of Color criterion supports communicating information through more than color alone.

A legend is useful only if the viewer can map its sample to the plotted series. Show the actual marker and line style beside each name, at a size comparable to the chart. Do not use tiny solid color squares to explain a graph whose meaningful difference is its dash pattern.

For the workshop example, reveal each name and its series sample together, then place the same marker on the first plotted point. Once all series appear, hold the complete chart. Direct endpoint labels reduce repeated journeys to the legend, although they require room near the right edge.

Make a grayscale copy for an illustrative inspection pass. Ask whether all three identities remain distinguishable at crossings, where markers are close and where a line runs behind a label. Grayscale is a useful diagnostic, not a complete accessibility test or a simulation of every visual condition.

If dashes collapse at compact size, increase their visible spacing or choose another encoding. If two markers look identical after export, simplify their shapes or separate the data into aligned small charts. Avoid solving one collision by hiding an entire category; keep the comparison available and explain any deliberate filtering.

During a reorder or emphasis change, move the label with its series or retain a stable reference. Do not turn all unselected series into an indistinguishable pale mass if their relationship is needed to interpret the selected one. A selected line can become slightly stronger while the others keep usable identities.

For a small portrait composition, a separate panel per category may read more clearly than three overlapping traces. That loses immediate overlap comparison, so preserve the same axes and tell viewers what to compare. Record the chosen tradeoff and inspect the final encoded chart in color, grayscale and at the intended compact size.