When choosing colours for use, it is important to remember that readability should be a priority. It is a critical first step in making our communication accessible to everyone.
Use high-contrast colours for text and background. Good examples are black or dark grey on a white or light coloured background, or white text on a black background. Printed material is most readable in black and white. If using coloured text, restrict it to things like titles, headlines or highlighted material.
White text over a coloured background should exceed the minimum 45% contrast ratio for readability.
For the safety colour palette, large type and graphics on yellow (pantone 130C), detour orange (152C) and pedestrian yellow/green (382C) should always be black. Large type and graphics on red (186C), green (pantone 355C), black, access blue (2935C) should always be in white.