Oh man! Be excited! I know this is the post you've been waiting for!
Ever take a look at that person shooting at you and wonder, Gee, I wonder what color they are on the inside? Well, wonder no more, my friends. I have compiled as thorough a list as any to satisfy your blood-raged needs, with Fiona Shep as your body-desecrating-guide.
(read: I got tired of having to look up the color of species' blood for fic purposes so I made a catalog and wanted to share)
Asari:
Asari appear to have a sort of red-pink color. It looks a bit violet to me in this light.
Batarian:
Batarians = humans with funky heads slapped on. Unsurprisingly, they have normal red blood. Not entirely sure how canon this is considered.
Collectors:
Collectors have blood like cockroaches. Gross? You betcha.
Geth:
Geth do not actually have blood. They have a white conductive fluid that most likely serves as lubricants for their inner machinery or keeps them at a stable temperature. Or it's white out. I'm not sure which.
Husks:
Black! And, unfortunately, despite falling apart like pinatas they are not filled with candy.
Krogan:
I got an interesting mix of red or yellow blood in krogans; all the ones with red blood, though, came from Mordin's loyalty mission. Similarly, if you shoot Grunt when you wake him up, he bleeds red around his jaw (forgot to screencap that one). All the rest had yellow blood, so I'm considering this the more canon standard as I believe it's mentioned elsewhere as the color.
Quarians:
There are currently no quarians that are hostile targets, so I'm going off of the dead quarians on Haestrom, which very obviously have red blood and bleed like stuck pigs. However, I'm wary of deciding this as canon because in other missions, such as Grunt's recruitment, they had turians that have very-much-canon blue blood lying in big ol' puddles of red blood. It may or may not be a placeholder blood effect, then, unless we get quarians to shoot at in ME3.
7/24/2010 UPDATE: A second playthrough reminded me that quarians *are* killed in the first mission on Freedom's Progress when the mech turns on them. Again, they have red blood, this time as they're actively being shot. I'm going to change my opinion on this to CANON.
Salarians:
Salarians, interestingly enough, got a differing range of green; the salarians who are murdered on Thane's recruitment mission have very dark green blood, but the ones you actually kill in this and other missions have lighter green blood. Weird.
Turians:
Turians, as mentioned before, have very bright blue blood, possibly from the presence of hemocyanin rather than hemoglobin according to ME Wiki. But hey, just in case you forgot, Garrus was super happy to have me upload an old save and get his pretty mug ruined all over again. FOR SCIENCE! \8D/
(Except not)
Varren & Vorcha:
Red, plain and simple.
Not pictured: drell (none to shoot and, as far as I'm aware, there are no scenes in which Thane and/or Kolyat bleed, though Feron is shown bleeding red in the comics), hanar, volus or elcor (none of them appear dead in game or are hostile targets).