In this work we address the issue of selecting and composing Web Services (WSs) considering functional requirements and transactional properties. We formalize the WS composition problem using the user query, the transactional properties of WSs and the composite WSs definition. We extends Colored Petri Net (CPN) formalism to incorporate transactional WSs properties. We present a CPN-WS selection algorithm that satisfies the user query functional conditions expressed as input and output attributes, and transactional properties expressed as a risk level. Our algorithm allows to construct a Colored Petri-Net representing a Transactional Composite WS.