How to set light and dark colours for a metamodel type

Diagrams can be viewed in a light or a dark theme, so every colour on an M2 type has two values: one for each theme. You set them in the Colours group of the type’s Appearance section. For the model behind this, see How colours work in light and dark mode.

Find the colour rows

Select the M2 element type or relationship type in the Explorer
In the Properties panel, open the Appearance section
Find the Colours group, with its Light and Dark columns:

Type	Rows
Element type	Fill, Border, Text, and Fold (shown only when Folded corner is ticked)
Relationship type	Line and Label

Each row has a Light swatch, a link toggle, and a Dark swatch.

Pick a colour

Click a swatch. A picker opens for that row and theme (e.g. “Fill · Light”)
Choose one of:
- Auto — clear the colour and let the theme decide (see below)
- a swatch under Presets, This metamodel (every colour already used by this metamodel’s types) or Recent
- the colour wheel
- a hex value typed into the box (e.g. #81D4FA), then Enter or click away

The change is saved straight away. The hex box saves only what you typed, so clicking into it and away again changes nothing.

Use one colour for both themes, or two

The symbol between the swatches shows whether the row is linked:

= Linked — a change on either side sets both. A row opens linked when both sides are the same.
≠ Unlinked — each side is set on its own.

Click the symbol, or tick Same in both themes in the picker, to switch. Linking two different colours copies the Light colour onto the Dark side; unlinking leaves both as they are.

Most fills are light pastels that read well on both canvases, so a linked fill is usually right. Lines and borders are where the themes differ: a colour that shows up on a white canvas can disappear on a near-black one.

Leave a colour on Auto

An Auto side shows the colour it resolves to, greyed and marked “Auto”, so you can see what you’ll get:

Row	Auto
Fill	The theme’s node background
Border	Charcoal in light mode, off-white in dark
Text	Black or white, whichever reads best on the fill
Fold	A shade of the fill: darker in light mode, lighter in dark
Line	Charcoal in light mode, off-white in dark
Label	The theme’s label colours

Leave Border, Text, Fold and Line on Auto unless the colour carries meaning — for example, a relationship type whose colour tells readers something. Auto adapts to both themes by itself.

Check both themes

The Preview below the colours draws a sample node or edge on the theme’s own canvas. Switch it between ☀ Light and ☾ Dark without changing the app theme.
A ⚠ appears next to a swatch when that colour is hard to read in its theme — text against its fill, a label against its background, or a line against the canvas. Hover it to see the contrast. The warning never stops you saving.