It looks to me more like the normal slightly oxidised urine to me. Urine turns rusty on a white underground as it dries.
Blood has a slightly different specific weight to urine, so in smaller quantities it either dries as small reddish dots in the middle of a puddle or as a reddish ring in a different tone on the outside of a urine patch. Only if there is a lot of blood in the urine or piggy is just dripping very bloody urine will you deep red/orange coloured spots.
If in doubt, you can test still wet urine with a test stick. However, if you have a tendency to anxiety, panic attacks or for obsessive monitoring of your piggies, then you'd better leave be - it can open a real can of worms for you, as it can make issues you have MUCH worse and take away all the joy you derive from your guinea pigs!