Looks like coolant, could be power steering or brake fluid. All three could have a very light reddish tint.
Like someone said above, you could get a good level check, then re-check the next time you have notable fluid loss.
If you get down and give it a good smell, you can sometimes ID the fluid. Brake fluid has an organic, oily smell with a faint fishy aroma, and while PS fluid will also smell like oil, itll have a burnt smell (and not really any fishiness). Coolant has a sweet smell, its pretty distinctive vs. the other two.
Youre probably running red coolant, but you can check the color, and if its actually green (or another color), you might be able to cross that off the list as the source (the fluid in the photo does seem to have a slight red/rusty hue).
Is the car intermittently running hot? Does is make odd noises when you turn the wheel? (especially at full lock) Do your brakes feel like theyre traveling much further down in the stroke on occasion? Ever see white smoke?