Accessibility: Contrast is too low between secondary brand colors and white

[jrchamp]

"Get This Book!", "Introduction" and footer icons have insufficient contrast
See: https://cnx.org/contents/Rko_umjB@6.4:MXTQeFW9@5/Introduction

The green color comes from here:

webview/src/styles/variables.less

Lines 11 to 12 in b7838e4

	@brand-secondary: #78b04a;
	@brand-secondary-dim: #6c9e42;

Please note that both the "secondary" and "secondary-dim" are too similar to the white background, failing to meet the minimum contrast of 4.5:1 for WCAG 2.0 AA compliance.