Try the following.
The variable (A:Light landing,bool) will return either 0 (off) or 1 (on). The <CaseValue> conditions will be used based on the variable's return.
Case 0 will be unlighted, Case 1 will be lighted:
Your supposition that the last <Element> in an XML script will override whatever otherwise identical <Element> precedes it is correct. However it isn't necessary to have two <Element> entries in this case.
Also, if you use the Luminous="Yes" attribute rather than the Bright="Yes" attribute, the color and strength of the Luminous is controlled by this red entry in the panel.cfg file: