Set font color of inactive textbox

Question

I've embedded an Easter egg in an app but to make it work, I store some text in an inactive text box. I can change the font color of active an active text box so it is the same color as the background. However when I disable the text box (to activate the Easter egg), the text becomes visible no matter what the font color is set. Is there a specific property I can set to control the inactive font color?