I will have to manage to shift colors with those grayscale values.
Fine in theory but I have never managed to get those working, not sure why. Maybe the chip needs to be supplied with the extra program voltagefor that.
Yes you will need buffering on the signal lines. I normally use the 74HTC04, these are inverting buffers so I use one to invert the signal and feed it too the inputs of the other five. Then you get five buffered outputs you can send to bunches of TLC chips.