COLOURING
When the pages are finished we export them as black/white .psd files for further use. On our website we place the pages as coloured line art pages. When opened in Adobe Photoshop, the space in between the panels is coloured the same light green as our website and the black is replaced with a very dark green. Just to make the lines less clear in case someone wants to print them (which isn't allowed of course). The page is then reduced in dpi and changed in size and saved as a .jpg file (quality 5) in order to be placed on our website. How to make such a website is a whole other subject on which there are plenty of books if you don't know how to.
You might not want a webcomic though, or you do but in colour. In that case you export the pages as a .psd file but without the dialog and text-balloons. Keeping these separate from the panels allows more freedom in case you want to have different versions of the comic, like a black/white version and a coloured one. Or like when the comic gets to be translated into a different language (for instance, a lot Dutch words tend to be larger than English ones which means adapting of the text-balloons).
The black/white bitmap mode is then converted into colour mode. It's best to use the CMYK mode as this is how it will be printed. However, this mode is larger than the RGB mode which might be too much for your computer (in case you have an oldie). If you work with RGB though, certain colours may look off when printed, such as pink and purple. Just take a random RGB picture and convert it into CMYK to see the difference. The other way round rarely gives problems (and is necessary if you want to place a CMYK file on the internet).
You can stick to just black lines or you can duplicate the lines in a second layer and colour them cyan. This is how printing has been done since they invented colour printing and it still works. The colour gets printed first and the black gets printed over this. Black on cyan only makes the black deeper. If you're into self-publishing however and you work has to be delivered in unlayered file, this doesn't matter and you an leave the cyan lines. The smartest thing to do is to always keep a layered .psd copy of all your pages, because you simply don't know what is needed in the future.
Another thing you might want to do before starting is to calibrate your monitor. Using the Adobe Gamma Wizard you can change the colours of your monitor to its most accurate setting. This should in principle get rid of a lot of the differences between monitor and printer. However, most people don't have a calibrated monitor and if you have this can actually cause problems with what you show on the internet. What looks great on your calibrated monitor may look very bad on the monitor of all of your readers. It's something to think about.
And then it's time to start the colouring. You can keep it simple or very detailed, it partially depends on your drawing style. Simply look at other comics to see what you like. We prefer to keep it simple, giving everything its basic colour and add some highlights and shadows to give it more depth using the dodge and burn tool.