You might have already resolved the problem but in case you haven't - I am still using the single panel color coding using range with a minor workaround
<single>
<title>Status</title>
<search>
<query>my search|eval range=if(Status < 1,"severe", "low") |table range Status </query>
<earliest>-60m@m</earliest>
<latest>now</latest>
</search>
<option name="classField">range</option>
<option name="field">Status</option>
</single>
Two things to remember :
The variable name should be range in the eval statement and also mention the same in classField option
The field you want to display as the value can be provided in the field option.
Hope this helps!
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