I'm writing a short story about robots and I wanted them to bleed coolant and thought the colour contrast would look good if it was yellow. I've read from multiple sources that coolant can come in many colours and others is just red and green. How can I find sources for mechanical/technology based information when I don't know much myself.
Learn to search efficiently
Often, people think it's easy to research something, and they will just tell you to 'google it'. That is not the case. Searching for an information is difficult, and may take a long time. Learn about the tricks, like excluding words from your google search, and first search for the vocabulary pertaining to that field. If you do it right, you may find your answer quickly and without much effort.
Ask a question
That is exactly what you just did. If you have a question about astronomy, ask it on a forum/stackexchange that is expert on that field. Lots of people will be glad to see someone have an interest for their field and answer your question.
It depends a lot on the kind of thing you want to know.
One excellent solution is to talk to experts. If you want to know how a car engine works, call up a local auto repair shop and ask to talk to a mechanic. If you want to know how police deal with crimes, call your local police department and ask for a ride-along. If you want to know how robotics work, look up universities that do robotics research and start calling the appropriate departments.
If you want to do research without talking to people, your best bet is published books that are supported by research (that is, they reference original sources in the back of the book). Libraries are excellent resources for this, as you can check the back of the book to see if it lists its sources.
Some good answers already on where to look including other SE sites, but I think there's a "Writing" question here about when you should look - and when you shouldn't. There's another way of dealing with this.
You'll run into people with deep technical knowledge who will take delight in pointing out what they think are errors and omissions - someone will ask why the coolant is yellow, or what it's cooling, or how you can be sure it's coolant and not hydraulic fluid, but this might not be your problem. If your narrator and the character observing it are not likely to know the answer, it's fine for the writer to say "I don't know" or for the narrator to say "No idea - it's just what [character] told me he saw".
If you've written the story so the character should know (for example a story written about a robotics engineer), you can still throw in a naive narrator to filter the story to the reader. They don't have to be stupid, just not well versed in the subject - despite years of medical experience, Watson never quite got the hang of Holmes' approach to deductive reasoning.
The most dangerous approach is to try to include specific detail in an area where you don't have firm background knowledge. Your audience (or at least some of your audience) will spot this and will concentrate on what looks like an error instead of on the story. Those of the audience who don't care about the detail will also be distracted - particularly if the detail isn't specifically relevant. It's the story that matters most.
"I thrust my spear at the figure and it bled yellow blood. I watched the strange blood form a pool on the ground, then turned away to find the rest of the tribe."