If you have a color device (like Nokia 7210, Nokia 7650 and Nokia 9200 Series Communicator), then you can view WAP services in colors. However, there is no color control in WAP so it is not much what you can specify. Actually, it depends on the device what elements can be defined in colors. Pictures (other than WBMP) can be viewed in colors (e.g. color wallpapers in Nokia 7210 and Nokia 7650).
With Nokia 7210 the text is black and links are blue.
With Nokia 7650 the text is black, links are blue and cached links are purple.
With Nokia 9200 Series Communicators you can use <em> tag to get red text and <strong> tag to get green text. Basic text is black and links are blue.