No problem - the first set of '<tr>' tags in your event format create the table row, so you need to define the class of the row in there. So now your event format will be:
<tr class="eventscat-#_CATEGORYID">
<td>
<strong> #_{D d M Y} #@_{- D d M Y}</strong><br/>
<i>#_12HSTARTTIME - #_12HENDTIME</i>
</td>
<td>
<strong> #_EVENTLINK</strong><br/>
<i>#_LOCATIONLINK</i>
</td>
<td>
<i>#_ATT{Teacher}</i><br/>
</td>
<td>
<i>#_ATT{Price}</i><br/>
</td>
<td>
<i>#_CATEGORYLINK</i><br/>
</td>
</tr>
Now in your custom CSS settings (I'm guessing that's what you mean in PlatformPro, but I've never used that theme) you need to add a different css class for each category id, so:
tr.eventcat-1{
background:red;
}
tr.eventcat-2{
background:blue;
}
tr.eventcat-3{
background:green;
}
etc
This will style the whole row of an event in a certain category. You'll find the category id numbers in your events menu under categories.
good luck.