To find out what color ribbons you need for the Bastet ritual, see Determining Festival Requirements.
For a list of ribbon makers, see the Bastet Inventory.
To make a ribbon, the concentration (not debens) of the paint must be 50, which means you will need to multiply your ingredients for making 1 deben of that paint by 5.
Since the catalyst ingredients (sulfur, potash, lime, saltpeter) do not affect the concentration, you do not need to multiply them, just add them as normal
Example:
Calixes' recipe for Sky Blue is 2 parts copper, 3 parts earthlight, and 5 parts cabbage juice - in that order.
Making 1 deben of this paint takes .2 copper, .3 earthlight, and .5 cabbage juice.
To get the 50 concentration paint for a ribbon of this color, she would multiply the 1 deben quantities by 5, so it would be 1 Copper, 1.5 Earthlight, and 2.5 Cabbage Juice.
So, with 1 copper, 2 earthlight, 3 cabbage juice and 1 silk cloth in her inventory, she would make sure the paint lab is set to make x1 batches.
She would then press the 'copper' button 5 times, the 'earthlight' button 10 times, and the 'cabbage juice' button 15 times in that order.
At this point, the 'Concentration' level on the pigment laboratory would read 50, and she would click the 'Make Colored Ribbons' button, and the ribbon would appear in her inventory.
It is possible to make multiple ribbons of the same color at once in a Pigment Laboratory that has the batch mixing upgrade. Simply switch the batch to x10, adjust your ingredient quantity, and be sure to be holding 10 silk cloth when you push the 'Make Colored Ribbons' button. This makes 10 ribbons of one color at once.
You must have them on during the ritual, so it is important not to put them on too early.