I have an aura component that is sitting on a grey background, so I need the field labels of my lightning:input boxes to have white text. But the text boxes themselves are white, so I need the text entry within the boxes to stay default black. No,  I cannot change the background on this page due to branding, etc.

Every solution I've tried so far has changed the text entry in the boxes to white while leaving the labels black, which is the exact opposite of what I need. Any ideas? Thank you!