Colors

Diagrammo has a small, closed set of named colors — red, orange, yellow, green, blue, purple, teal, cyan, plus the neutrals gray, black, and white. Use them anywhere a color is accepted, and never write hex codes. There is no way to add a twelfth name; crimson, navy, and #3b6ea5 are all rejected.

The actual shade is resolved from the active palette, so the same blue looks different in Slate than in Nord — but it’s always that palette’s considered version of the hue, never a clashing primary. black and white are theme-relative: each palette picks near-darkest / near-lightest values that stay distinct from the canvas, which means black is the strongest mark you can make on a light theme and nearly invisible on a dark one. white is the exact reverse. Neither is a fixed ink.

The active palette is chosen at render time, not in the diagram source — --palette <name> on the command line, or the palette picker in the app. The palettes that ship are slate (the default), nord, atlas, blueprint, catppuccin, tidewater, and tokyo-night. See Exporting diagrams for how to set it, along with the light/dark/transparent theme.

Choosing a color

Naming a color is easy. Deciding which one is the actual work, and the answer is almost always about how hard you want an element to push.

What advances, what recedes

Every palette is tuned so no series shouts, so the differences are smaller than in a raw RGB set — but they are consistent, and they are theme-dependent:

• gray is the recede color, in every palette and both themes. It carries the least color of any hue name — measurably so; in every shipped palette, in both themes, gray is the lowest-saturation entry of the eight hues plus itself. That is why it recedes: it has no hue competing for attention, so it reads as context rather than as a category. It is not necessarily the palest color; Nord’s light gray is quite dark. Gray means “still here, not the point.”
• blue, purple, and red advance on a light theme. In every shipped palette, the strongest-contrasting non-neutral against a light canvas is one of these three. If one element must be read first, it belongs on one of them.
• yellow is the weakest color on a light theme and one of the strongest on a dark one. In nearly every palette, yellow has the lowest contrast against a light canvas of any non-neutral, and the highest against a dark one. red runs the opposite way — solid on light, and the weakest non-neutral on dark in nearly every palette. Never put your most important series on yellow if the chart might be exported light, or on red if it might be exported dark — and re-check any color-carried emphasis after switching themes, because the ranking genuinely changes.
• orange, green, teal, and cyan are the middle. Reliable for categories that need to be told apart, unreliable for “look here first.”

What gray is for

gray is the background voice. Use it for the elements a chart needs in order to be honest but doesn’t want to argue about:

• the comparison baseline — last year’s line, the control group, the plan you’re measuring against
• the residual bucket — “Other”, “Uncategorized”, everything below the fold
• the parts of a structure that provide context rather than carrying the message

Doing this deliberately is the single highest-leverage color decision available, because it is what makes everything else look emphasized without you having to shout.

Building emphasis

Emphasis is contrast within one chart, so it has to come from the per-element channel:

treemap Fleet Cargo by Hold

tag Emphasis as e
  Focus blue
  Context gray

Rum 320 e: Focus
Silk 210 e: Context
Spice 180 e: Context
Salt 140 e: Context

A tag group is the general-purpose tool: declare the group once, then attach a value to each element. It maps meaning to color across the whole chart and adds a labeled legend, so the emphasis is explained rather than merely applied. Where a chart type takes a bare color token on an element or a series, that works too and is quicker; tag groups are the form that works nearly everywhere. See How DGMO thinks for where each form applies.

One caution: color is a scarce resource and emphasis spends it. If three of five elements are “emphasized”, none of them are.

The limit you will hit

fill-tint, fill-solid, and fill-outline are chart-wide — they set the fill treatment for the entire diagram, not per element. That makes them a tone control, not an emphasis control. You cannot solid-fill one bar and outline the rest, so the thing emphasis actually requires — contrast within a single chart — is not available from the fill family. Build emphasis from color choice and tag groups instead.

For genuine emphasis — pushing one element back without recoloring it — two chart types ship a dim / highlight directive that fades everything else while preserving each element’s own hue (a red flow that recedes is still red). sankey has both dim <name> and highlight <name>; family has highlight <name>, which dims everyone outside one person’s bloodline. Both bake into the exported image — no hover needed. On every other chart type there is no de-emphasis directive yet, so “recede” there still means assigning gray.

Accessibility

Treat color as a secondary channel, never the only one. Palettes are tuned for a single perceived weight, which is good for looking calm and bad for telling hues apart under color-vision deficiency — blue and purple in particular sit close in hue and separate weakly under deuteranopia, and tinted fills push them closer still.

The rule that follows, stated for family and true everywhere: the legend, not the hue, is the guaranteed channel, because its entries carry text. So when accessibility matters:

• Carry the distinction on a tag group, which produces labeled legend entries, rather than on bare color tokens which may not.
• Separate important categories by lightness as well as hue — pair a light-theme strong color (blue, purple, red) against gray, not blue against teal.
• Keep the number of color-carried categories small. Beyond a handful, no palette separates reliably for anyone.
• Check the chart in both light and dark, since the contrast ranking flips between them.

Named Colors

Every name, shown across the palettes that ship: