Thanks for the endorsement Peter!
This is an interesting discussion. You will see on my blanks list that I have split mahogany (genus Swietenia) into two basic categories, essentially light and dark grade, for this very reason. Neil is spot on, true mahogany is hugely variable timber, from pale, light and fine textured to moderately heavy, coarse textured and dark in colour - in all combinations!
As a general rule, paler is pretty dull and darker rather more interesting. It certainly is a timber that is better appreciated in the large-scale of a piece of furniture rather than the small scale of a pen - but there are always exceptions. In fact, I've just got hold of a lump of mahogany that looks really nice and once I've finished properly assessing it I'll include it on the blanks list if it proves worthy
And while I'm whittering on about my favourite subject, there is the original holy grail, Cuban mahogany, which is now to all extents commercially extinct but that really is something good if you can acquire it from any reclaimed source. Beautiful to work with an the colour improves with age.
Mark, have a look in the Buy & Sell and look for a poster called lignaterrae he has some great blanks.
Peter