In the meanwhile, you can, of course, update formatting conditionally with an applescript.
These colors are illustrative (certainly not recommended :-) but the code may give some idea of how to start ...
Code:
property pstrColumnName : "Priority"
property plstCheckedColor : {65530, 49344, 49344}
property plstHiColor : {0, 0, 65530}
property plstMedColor : {0, 0, 0}
property plstLoColor : {0, 65530, 0}
property pstrGutter : "item-gutter-color(com.omnigroup.OmniOutliner)"
property pstrFontColor : "font-fill"
tell application "OmniOutliner Professional"
tell front document
repeat with oRow in rows
-- set gutter color by state
set oStyle to style of oRow
if state of oRow is checked then
set varGutter to plstCheckedColor
else
set varGutter to missing value
end if
set value of attribute pstrGutter of oStyle to varGutter
-- set text color according to value of a numeric column named "Priority"
set oCell to cell pstrColumnName of oRow
set lngValue to value of oCell
if lngValue is missing value then
set varTextShade to plstMedColor
else if lngValue ≥ 5 then
set varTextShade to plstHiColor
else if lngValue ≤ 2 then
set varTextShade to plstLoColor
else
set varTextShade to plstMedColor
end if
set value of attribute pstrFontColor of oStyle to varTextShade
end repeat
end tell
end tell