Unfortunately, there isn't a simple solution to this problem. It will require considerable effort and perseverance.
One approach is to enhance the Text class by including a static StyleSheet property (e.g., styleSheet:StyleSheet = null). Then create an array containing specific styles supported by Flex:
listOfStyles:Array = ['fontSize', 'color', 'fontWeight', 'fontFamily', 'fontStyle', 'textDecoration'];
Next, you need to initialize the StyleManager.selectors by defining selectors for usage. Essentially, locate the "A" tag and apply the aforementioned listOfStyles to it, followed by creating a new CSSStyleDeclaration for each style.
This enhancement enables the application of the specified styles to the htmlText property of your extended class. While this allows for diverse styles to be set for anchor tags upon loading using an external stylesheet, implementing a rollover effect where each link changes color on hover within the HTML presents challenges. The MouseEvent.MOUSE_OVER would be applied to the entire class rather than individual HTML elements. To address this, detecting if the mouse is over an anchor in that HTML text would be necessary, involving determining the text range - which can be labor-intensive. I encountered a similar challenge when incorporating emoticons into text flow (an area where Flex's HTML implementation lacks support), and it was quite complex.
It's possible that Flex 4 may offer improved native support for such tasks, although I haven't delved into that specifically.
While I don't have a quick fix for your issue, I hope this provides some insight into the matter.