In CMYK the lightest colour is normally added first, with the overlay of the 2 other colours, cyan and magenta the colours mix and create different colours. Black is used because it keys together the other colours and refine the shadows and it adds in extra depth.
There are multiple ways to apply colour in illustrator, clicking show options on Colour allows you to adjust the CYMK levels individually which is great if you're wanting to do something related to screen-printing and commercial.
You can create swatches by dragging in a colour from a object into the swatch tool bar.
Alternatively use the colour picker.
It's good practice to get rid of all the swatch colours to allow you to then work from fresh and make up your own swatches so you don't mess up printing.
If you select Small list view you're able to see what your colours are, (For example: CYMK colours, and registration marks.) and what they are called. Only use registration marks if your creating printers marks.
Then add in your own, when you create them this way you have full control of the CMYK levels and whatever colour mode is necessary. Once created it'll take on the swatch name, which will be the amounts of each colour. It's best to keep them like this so you know whats in them.
You can pick a colour in the Colour tool bar and then create a new swatch from them too.
You can also use the colour picker to create colours that you can create swatches out of.
You can also have a pre-existing art-work piece, you can then get all the colours from that piece of art work (if it's created in illustrator), by going to the swatch options and clicking 'Add used colours'/'Add selected colours'. This then adds all the colours.
Once that's done, the swatches should all have a little triangle, this means it's globally selected and if I was to edit this swatch it would edit the object's colours on the document. So If i had a black box that was globally linked, I could change the black on the swatch bar to a red and the box would then become red. This only works if Global is selected.
If i have one of the global objects selected I'm able to then work with tints, once selected. This allows me to work better within very limited palettes.
I can then add these tints to the Swatch list by clicking Add to Swatch from the Colour options. What is great about this is that if I was to change the original colour the tint as well will also change automatically.
This doesn't just work for one tint, but it will be applied to all so you can create a range of tints.
Spot colours are colours that aren't mixed with CMYK, they can be used for things such as a one or two colour print job. So you'll be using just two inks. Cheaper then CMYK. Doing this you can get special colours that aren't able to be produced with CMYK, such a fluorescence colours. Such as getting a colour that's for a brand, such a the colour used for the Sainsbury's. This is achieved by using a spot colour, it gives you consistency. (Pantone)
You can find such spot colours within the Pantone Solid coated range, you can tell that they're spot colours by the little triangle in the corner of each colour it has a little black spot to signify that.
To gain more tonal range you can also adjust the tint of them. This is alot better of the CYMK method, using just one spot colour you can achieve more colours with tints.
If I want to transfer my library of swatches for a client/project, for a later use I can save my swatch library to transfer to Indesign and Photoshop I click 'Save swatch library as ASE' (When doing this save the file with the rest of the work so it's easy to access instead of it been hidden with a file somewhere)
If I want it to be transferred to another illustrator file I save as the option below.
If I then want to access this in a new document I simply have to follow this route within the Swatch tool bar:
