Side note: Some themes, Anomaly, for example and also Formal White (since MDL-31712) already have own alternation CSS selectors.

Also, I'm not sure if base or canvas should define them at all (or perhaps yes defaulting to bg-color = none or so), just to allow others to know about their existance.

Or, alternatively perhaps all core themes should specify them, but always independently. From my knowledge base and canvas use to be color-free (detail-free). And this, although really important because it helps a lot visually, it's just one color detail.

So, sided-mind here... I leave this on expert hands (anybody but me). Ciao

Yes, Eloy.
I thought about the same problem.
The alternation of colors is a general issue but the particular color of each theme is a not general at all.
I see two ways:
-> the one you proposed: all core themes should specify the row highlight independently.
-> each theme has to provide two colors in its setting page (or hardcoded in its config) and the general highlight will use them

IMHO your solution is faster unless deeper afterthought about themes is going to come.

i think the row colour alternation is a general accessibility issue so this should be addressed in core - as far as readability should be ensured.

I wrote a proposal of general solution in:
https://github.com/kordan/moodle/tree/MDL-31712_generalsolution_master
or here:
https://github.com/kordan/moodle/compare/master...MDL-31712_generalsolution_master
if you prefer

Aparup and Mary
I wrote my proposal of general management of each color related problem in http://moodle.org/mod/forum/discuss.php?d=201604

Thanks Danielle

This issue had never been Triaged so this has not been picked up and could do with going into 2.4...

It's triaged now.

I've integrated this now, thanks Mary.

At first I did not notice a difference in colour whatsoever. I then looked at the commit and then at the CSS being applied on the page for rows r0 and r1 and saw they were using #F0F0F0 and #FAFAFA specified in the diff. However, really these colours appear identical. I am failing because I do not believe the difference in colours is enough for the human eye to distinguish between the two, not because the logic failed.

Mark, I think you may need to get yours eyes tested. This is a perfect combination of row background colour.
See attached image.

Mary: I looked at this too, but I couldn't see it either!

Do either of you see the light-grey background when you hover over the comments here? Because that is the same colour #F0F0F0 which is what I have for row r0. What if I keep that for r0 and make the r1 row white? Would that be better?

There are two versions of the Web Content Accessibility Guidelines to verify if two colors are well contrasted or not.
I googled "html accessibility color contrast analyser" and, for instance, I found: http://www.colorsontheweb.com/colorcontrast.asp
That site declares that #F0F0F0 and #FAFAFA are not ok.

Un'alternativa sarebbe bene allora

@Dan

I've altered this so only r0 uses the background-color, this measn r1 will retain the default color (white).

Sam pointed out that this rule is defined in standard theme:
.generaltable .cell

I'm passing this based on other themes, I think we need to deal with the issues from this change in a new issue.

Congratulations! Another bug solved.. only another 7330 to go, thanks for contributing to contributing to 0.8% of all bugs being fixed this week!

ciao
Dan