I agree with the other two posts, MIL-H-5606 hyd fluid(red) is used for strut servicing. And on large aircraft Skydrol(bright purple) is used for hyd. systems. However they are both perfectly capable Hydraulic fluids, the main difference being 5606 burns, and Skydrol will not support a flame no matter what you do to it. Skydrol is used in large planes with a lot of fluid because if a fire were to break out the last thing you want is 3000 psi of "5606 fuel" to be dumping itself on the fire. However Skydrol has its draw backs, it sucks to work around, burns skin on contact (not real burns just irritation), the worst place to have it is in the eyes, makes you go blind till you get it out, it also peels paints and melts plastic quite readily. So 5606 is often used in its place when large quantities aren't required, such as LG
struts or HTCS (Hydraulic Torque Compensation Systems) on the PW150's on the Q400's.
That fluid looks to be coming from where I would expect the Nitrogen servicing point to be on that gear, never having worked on a 757. Should be plenty more fluid where that's coming from on landing at his destination. Of course that brings up an interesting question I haven't had answered yet, what happens when a plane lands on one or more "flat" struts? Especially a plane of that size. I would assume it would make for a somewhat rough landing. Anyone know?