david upshaw: I think that is because most players who play as black does not look to the long term and only looks for the highest points for the first 1-3 moves.
If black starts on the same color square as white, black will then be able to "block" spaces so white can't jump to them and can do more planning towards the end of the game.
For example, white might see that they can jump to 23, then 99, then 97 - but if I can get and "block" the 99, they will be stuck with fewer points... or even blocked where they can't move.
Taking a look at my 61 wins - 48% are from black (29) and 52% are from white (32) - so basically even
From my 25 loses, 13 black & 12 white - so again, almost even.
So at least from my experience, I find both sides close to being even.
... and before someone says it, each game is different and sometimes there are exceptions to always starting on the same color as white. Sometimes there will be a 99 - 98 - 97 - 84 type of first 4 moves starting on the other color which you can't pass up... but for the most part, being black & starting on the same color helps a lot.