How to display risk on a spectrum low to high?

If you're ok with using plug-ins there's a nice selection from Vuram in the AppMarket including this example: 

Thanks Stewart, I should have included that detail... trying to avoid using a Plug-in (got to love restrictive InfoSec red tape) you've highlighted what I've been running into - several great gauges, sliders, in the AppMarket.

Ah, ok, so it's not as intuitive but you can add reference lines onto column/bar charts (depends if you want the bar to be vertical/horizontal), have the reference lines as the thresholds you describe and the colour your column/bar red/amber/green as appropriate...that's one suggestion...I'll see if there's anything else a bit more intuitive

Like this...

Something like this with richTextDisplayField works? If so below is something that might help. You can try to write in a more efficient way.

a!localVariables(
  local!value: 77 / 10,
  local!items: (enumerate(10) + 1),
  {
    a!richTextDisplayField(
      marginBelow: "NONE",
      align: "CENTER",
      value: a!forEach(
        items: local!items,
        expression: {
          a!richTextIcon(
            icon: if(
              fv!index <= local!value,
              "circle-large",
              if(
                (fv!index - 0.5) <= local!value,
                "adjust",
                "circle-o-large"
              )
            ),
            size: "LARGE",
            caption: fv!item * 10,
            color: if(
              fv!item <= 3,
              "POSITIVE",
              if(
                and(fv!item > 3, fv!item <= 6),
                "#F4C430",
                "#FF0000",
                
              )
            )
          ),
          char(32)
        }
      )
    ),
    a!richTextDisplayField(
      marginAbove: "NONE",
      align: "CENTER",
      value: a!richTextItem(
        text: local!value * 10,
        size: "LARGE",
        style: "STRONG",
        color: "SECONDARY"
      )
    )
  }
)

Have a look at the KPI components ...

https://docs.appian.com/suite/help/24.2/kpis-pattern.html

It has been updated in the latest version (24.2) but provides a good out of the box way of handling things like this. I use it a lot!

You can customise it dependent on the nature of the data and also add extra context to help the user. Customisation can include colour schemes and wording dependent on where the number lands in the spectrum. 

Progress bar field

a!forEach(
  items: { 30, 60, 90 },
  expression: a!progressBarField(
    percentage: fv!item,
    style: "THICK",
    color: a!match(
      value: fv!item,
      whenTrue: fv!value <= 33,
      then: "#FFFF44",
      whenTrue: fv!value >= 67,
      then: "#FF4444",
      default: "#44FF44"
    )
  )
)

Research KPI, if I'm not mistaken there is a component now (not sure though) but if you navigate to the pattern tab in the interface page there are a lot of KPI examples you can copy or mimic