phoi_Color tracks by place in folder hierarchy.lua

-- USER VARIABLES
colorOffset = -30
-- the offset to apply to the color of each track for each generation down the hierarchy.
--  Set to negative colors to make children darker than parents and vice versa.


-- NAME
local scriptName = ({reaper. get_action_context()})[2]:match("([^/\\]+)%.lua$") -- generate default scriptName from file

--FUNCTIONS FOR DEBUG
function msg(msg)
  reaper.ShowConsoleMsg(tostring(msg) .. "\n")
end

--- FUNCTIONS

function getSelectedTracks()
  local tracks = {}
  local tCount = reaper.CountSelectedTracks(0)
  for i = 1, tCount do
    tracks[i] = reaper.GetSelectedTrack(0, i - 1)
  end
  return tracks
end

function getTrackLevel(track) -- get how many "levels" down the hiearchy the track is; 0 for parents, 1 for first-generation children etc.
  local level = 0
  local found = false
  local cur = track

  while not found do
    local up = reaper.GetParentTrack(cur)
    if up == nil then -- if parent doesn't exist
      found = true
      return level
    else
      level = level + 1
      cur = up
    end
  end

end

function offsetTrackColor(track, offset)
  local prevColorNative = reaper.GetTrackColor(track)
  local prevColorR, prevColorG, prevColorB = reaper.ColorFromNative(prevColorNative)
  local newColorR = math.max(math.min(prevColorR + offset, 255), 0)
  local newColorG = math.max(math.min(prevColorG + offset, 255), 0)
  local newColorB = math.max(math.min(prevColorB + offset, 255), 0)
  local newColorNative = reaper.ColorToNative(newColorR, newColorG, newColorB)
  reaper.SetTrackColor(track, newColorNative)
end
----- END OF FUNCTIONS


function main()
  reaper.Undo_BeginBlock()
  for i = 0, reaper.CountSelectedTracks(0) - 1 do
    local tr = reaper.GetSelectedTrack(0, i)
    local trLvl = getTrackLevel(tr)
    offsetTrackColor(tr, trLvl * colorOffset)
  end

  reaper.Undo_EndBlock(scriptName, -1)
end

reaper.PreventUIRefresh(1)
main()
reaper.PreventUIRefresh(-1)
reaper.UpdateArrange()