How can I set text color inside tikzstyle? I tried as shown below, but surely that is not the correct thing.
I can do it seperately in each node, as shown here, but I want to declare it globally.
\tikzstyle{cloud} = [draw, ellipse,fill={rgb:red,91;green,146;blue,230}, node distance=4cm,
text width=5em, text centered, minimum height=2em, text color=white]

text=white? Look at manual sectionText parameters: Color and opacity– Ignasi Nov 29 '13 at 16:39