Can you please help me write a scan to search for Heiken Ashi color change from green to red / red to green for  daily and weekly time frames. 

If you have Color Based On set to Net Change than going from green to red would as follows.

O + H + L + C <= O1 + H1 + L1 + C1 AND O1 + H1 + L1 + C1 > O2 + H2 + L2 + C2

And going from red to green would be as follows.

O + H + L + C > O1 + H1 + L1 + C1 AND O1 + H1 + L1 + C1 <= O2 + H2 + L2 + C2

If you have Color Based On set to Open vs Close then going from green to red would be as follows.

O + H + L + C <= XAVGO3.1 + XAVGH3.1 + XAVGL3.1 + XAVGC3.1 AND O1 + H1 + L1 + C1 > XAVGO3.2 + XAVGH3.2 + XAVGL3.2 + XAVGC3.2

And going from red to green would be as follows.

O + H + L + C > XAVGO3.1 + XAVGH3.1 + XAVGL3.1 + XAVGC3.1 AND O1 + H1 + L1 + C1 <= XAVGO3.2 + XAVGH3.2 + XAVGL3.2 + XAVGC3.2

You would set the time frame of the Condition Formula to Daily for the daily formula and to Weekly for the weekly formula. You can use the TimeFrame drop-down menu in the Edit Formula window when creating or editing the formula to adjust its time frame.