Hi Chandra,
Here is a CSS rule you can try that overrides the CSS that’s coming from Lightning’s app.css file:
.forceStyle .required{
color:#706e6b;
font-weight: inherit;
}
The field labels looks like they’re supposed to, if you’re not in Lightning, because the base Lightning styles aren’t loaded. But in Lightning, some Lightning style rules are coming into the mix, and the color of the text is set to red, and the weight is set to 700 (bold). The strange thing is that those rules don’t match what you see in standard Lightning field labels, so it looks to me like there’s some unexpected interaction between the different stylesheets.