You can't put JS inside the XML, you have to add JS files to appserver/static and reference them from the dashboard with <form script="myjs.js">
However, if you're just looking to colour boxes, then see this example dashboard that uses conditions to set colours - 3 examples.
You can use either of the fist two techniques to colour the box
<dashboard>
<label>colour_box</label>
<row>
<panel depends="$hide_css$">
<html>
<style>
#verdict rect {
fill: $verdict_background$ !important;
}
#verdict text {
fill: $verdict_foreground$ !important;
}
</style>
</html>
</panel>
<panel>
<single id="verdict">
<title>Verdict - use CSS to style box</title>
<search>
<query>| makeresults
| eval verdict=mvindex(split("Pass,Fail",","), random() % 2)
</query>
<done>
<eval token="verdict_background">if($result.verdict$="Pass", "green", "red")</eval>
<set token="verdict_foreground">black</set>
</done>
</search>
<option name="colorMode">block</option>
<option name="drilldown">none</option>
<option name="height">60</option>
<option name="rangeColors">["0x53a051","0xdc4e41"]</option>
<option name="rangeValues">[0]</option>
<option name="useColors">1</option>
</single>
</panel>
<panel>
<single>
<title>Verdict 2 - define range based on pass/fail verdict</title>
<search>
<query>| makeresults
| eval verdict=mvindex(split("Pass,Fail",","), random() % 2)
| eval range=if(verdict=="Pass", "low", "severe")
| table verdict range
</query>
</search>
<option name="colorMode">block</option>
<option name="drilldown">none</option>
<option name="height">60</option>
<option name="field">verdict</option>
</single>
</panel>
<panel>
<single>
<title>Time Age - more than 3 days is red</title>
<search>
<query>| makeresults
| eval timestamp=now() - (random() % 7) * 86400
| eval range=if(timestamp < relative_time(now(), "-3d"), "severe", "low")
| eval timestamp=strftime(timestamp, "%F %T")
| table timestamp range</query>
<earliest>$earliest$</earliest>
<latest>$latest$</latest>
</search>
<option name="drilldown">none</option>
<option name="field">timestamp</option>
<option name="height">60</option>
<option name="refresh.display">progressbar</option>
</single>
</panel>
</row>
</dashboard>
