There's nothing wrong with an immediate b5, and there's only one move for you to reply with. Where's the problem?
The only way to avoid it is to stop playing the Ruy Lopez, and you can't capitalise because it isn't weak.
Normally b5 isn't normally immediate simply because white isn't really threatening to win a pawn until he supports his own rook.
I know I only have one response. It was just one of those things were you don't see 4. . b5 in any of the intros. to the Ruy that you see at my level (Idiot's guide to openings, etc.) Thought there might be something I was missing that better players use in response to make that an unpopular line at higher levels.
At your level, you could try meeting 4. ... b5 with:
6.Ng5 is simply a stupid move here- it doesn't work because the bishop is on b3, not c4: 6...d5 7.ed5 Nd4, and Black is already better. Actually this is a bad Fritz variation (with the bishop having retreated to b3 instead of f1) and also Black having an extra move (...a7-a6) for free.
In short, yes, it's recommendable to play like that if you want to lose. Ac trually this is the case ion your example in the end of the "blue" variation: white is rather lost after either 9...Qxc7, or 9...Qd5. After 8.d6? the move 8...Qxd6 is also very good for Black. Could you recommend something less crappy?
White should simply play 6.0-0, which will transpose to the (Neo)Arkhangelsk, since he has no better move to punish Black's move order (6.d4 Nxe4!)
So I've been playing the Ruy Lopez as white in a run of recent games and have been running into trouble with this line which frequently occurs at my level of play.
I know 3 . . a6 4. Ba4 is the Morphy Defense. I also know, I think, that black usually doesn't follow with b5 (could be wrong). Unfortunately, at my level, they do and it's been causing me problems.
Any suggestions on how to either avoid this situation or to capitalize as white in some way that I just don't see.
Note: this is not a current position in any of my live games, but, rather, something I encountered 4 or so times in the last month.
Thanks -
CMI