Pulse

local chartbl = {"*","%","@"}
local colortbl = {colors.blue, colors.lightBlue, colors.cyan, colors.green, colors.lime, colors.yellow, colors.pink, colors.magenta, colors.purple}

local curCol, incCol, reverse, maxx, maxy = 1, 1, false, term.getSize()

local function advClear( c, b, t )
    term.setBackgroundColor( b )
    term.setTextColor( t )
    for y = 1, maxy do
        term.setCursorPos( 1, y )
        term.write( c:rep( maxx ) )
    end
end

while true do
    for theChar = (reverse and #chartbl or 1), (reverse and 1 or #chartbl), (reverse and -1 or 1) do
        advClear( chartbl[ theChar ], colortbl[ curCol ], colortbl[ curCol + (reverse and -1 or 1) ] )
        sleep( 0.05 )
    end
    for theChar = (reverse and 1 or #chartbl), (reverse and #chartbl or 1), (reverse and 1 or -1 ) do
        advClear( chartbl[ theChar ], colortbl[ curCol + (reverse and -1 or 1) ], colortbl[ curCol ]  )
        sleep( 0.05 )
    end
    curCol = curCol + (reverse and -1 or 1)
    if curCol == 1 or curCol == #colortbl then
        reverse = not reverse
    end
end