This is just my opinion for what it is worth...
I have played with some of the various stuff out there... and this is what I have found from my own experiences... now remember I am no expert...
If you are looking for the bright colors of the rainbow, I suggest either the Chestnut or Artisan Analine Dyes sold by CSU.. they are alcohol based and do not raise the grain.. also since they are alcohol based you can dilute them a bit to get a more translucent color wash... I have also found that using them on real curly or burled woods gives the best results.. since these woods absorb dyes at different rated between the burl/curl and the normal wood, buffing them with 0000 steel wool after the dye has dried changes the character of the dye.. making parts of it light and the other parts stay dark... very nice contrasts...
If you are looking to enhance the color of your blanks with natural wood colors, I recommend the TransTint brand of dyes... available from just about all the major suppliers online... again an analine dye that can be made more translucent by thinning with alcohol...
<b>NOW HERE IS THE BIGGIE.... NO WHERE... I MEAN NO WHERE...</b> did you see me mention the term stain.... Stains are made up of ground up pigments suspended in a carrier medium... they need to be shaken or mixed before use to reconstitute the solution... they also are more of a surface coloring agent that also fills the pores of open pored woods like walnut, oak, etc. Stains will look more muddy than dyes.. and tend not to be as light fast as dyes... they also take longer to dry because the pigments need to dry not just the carrier...
Dyes are in total solution and soak into the wood, not on the surface, they dry quicker (if alcohol based) and are more light fast and tend to be brighter and more accurate in color.. Dyes can also be mixed to obtain new colors since there are no pigments to worry about... dyes can be used on top of each other to alter the appearance of the bottom coat... if you try this with a stain it does not work..
Dyes are also available in a water base, but I really don't like them because they raise the grain and take longer to dry.. not bad if you are doing flat work.. but a real PIA for a pen turner...
I am also experimenting with some of the more light fast artist inks to see what they can do... as I get a better experiment base, I will post it here along with product or type recommendations.. I just picked up some translucent acrylic artists ink... supposed to be light fast and quick drying... I am going to play with it a bit today.. got red, yellow and blue...
These are strictly my opinions and what has worked for me.. take it for what it is worth.... the best thing I can recommend is that you experiment with what you think will work for you... but remember, success on one piece of wood does not make a valid experiment.. each species will react differently to the materials you will use..
For instance, we all have a problem keeping purpleheart 'purple" I found that a diluted red analine wipe will keep it looking good even months later when other pens have started to turn.. YA GOTTA EXPERIMENT... LOL